Bernalillo Public Schools

Bernalillo Public Schools

Middle School Distance Learning

Science Grade 7

Week 1 Dates: April 20-24

Cell Systems

Learning Target: I can understand how cell structures determine their function.

Activities – Complete the following activities during the week to reach our learning target by Friday. If you choose, take a picture of your work and text or email the picture to your teacher.

Read the article below and complete the activities at the end.

The Cells That Make Us

“Mom, I’m hurt,” said Mike.

“What happened?” asked Mike’s mom.

“I stumbled and fell while playing football at the playground today. I scraped my knee,” said Mike.

“You poor dear. Here, let’s put a Band-Aid on your knee,” said his mom.

Mike’s mom gingerly wiped his bleeding knee with a wet cloth and pasted a Band-Aid on it. Mike wondered aloud, “Our bodies are made of arms and legs. The arms and legs are made of blood and bones. But what are these blood and bones made of?”

Mike’s mom replied, “Everything in our body is made of small units called cells. Think of it this way. Just like hundreds of thousands of bricks form a house, millions of cells form our muscles, bones, skin, and hair—eventually coming together to form the human body.”

As Mike looked at his bandaged knee, he wondered, “Wow, can I see these cells?”

“You cannot see most of your cells with the naked eye,” said his mom. “A cell is small. A cell is the smallest unit that can be said to be alive. You can see a lot of cells through a microscope.”

“So, every part of my body consists of cells?” Mike said.

“Yeah. Not just your body, mine too,” said Mike’s mom. “Your pet dog, Tommy? He’s made of cells. Your friend Jim’s cat? She’s made of cells, too. The lions we saw on safari last year, the spiders in our storeroom. Every creature on Earth is made of cells, just like you and me.”

“Wow, so an ant or an amoeba is built up of cells, like Lego blocks?”

“The ant, yes, sort of like Lego blocks. But some creatures have just a single cell, like an amoeba. They are called unicellular organisms. Other creatures, like us human beings, are collections of cells. These are called multicellular organisms. Multicellular organisms can range in size from brown algae to large animals like elephants and whales, which have trillions of cells.”

“But what does a cell look like?”

“A cell consists of different parts.”

“Like what?”

“So you know how you have different parts of your body that are responsible for different activities? For example, your legs help you move, your stomach helps you in digestion, and your eyes help you see. Well, different parts within cells are responsible for different functions. These different parts perform the activities that keep the cell alive.”

“Wow, so how does a cell stay alive?”

“The different parts of the cell work together to keep the cell alive. Many cells have a nucleus. The nucleus is the ‘brain’ of the cell. It controls and coordinates all activities of the cell. The nucleus is surrounded by the nuclear membrane, which helps to protect the nucleus. In addition to the nucleus, many cells have some other parts. All the parts of the cell are contained within a cell membrane. This is the outer covering of the cell. The cell membrane can allow certain substances, like nutrients and water, to enter the cell. It also can let out waste and even block out some unwanted substances.”

“It’s so cool that the cell membrane can let in some things and block other things.”

“Yeah. Then, between the nucleus and the cell membrane, there is the cytoplasm, which is a gel-like fluid that fills the area. And some other parts of the cell are located in the cytoplasm. Like the nucleus and cell membrane, each part has structure and function.”

“Wow. Cells are like machines! What powers them?”

“Energy production usually happens in a part of the cell called the mitochondrion. Not all cells have mitochondria, but a lot of cells do. Mitochondria are usually round or oval-shaped. Sometimes they are shaped like kidney beans. Mitochondria convert food into chemical energy for the cells.”

“Do we use this energy, too?”

“Absolutely. The accumulated energy in a lot of the trillions of cells in the average human body help to give us energy. It helps us have the strength to move our arms and legs, to think, and to live.”

“Wow. So the cells work together?”

“Yeah. A group of human cells band together and form a tissue. There are four main types of tissue in humans. Connective tissues include blood or bones. These form connections between structures in the body. Muscle tissues form muscles, which help us move. Nervous tissues are in the brain, spinal cord, and nerves. This type of tissue helps to control many body activities. Epithelial tissues are tissues that line or cover the different parts of the body. This type of tissue has various functions, such as protecting and filtering.”

“So many cells make up different types of tissues, and the tissues have different functions in our body?”

“Exactly! The tissues are specialized for different functions, so the cells of one type of tissue work together in unison. For instance, all the cells in the muscle tissue in your calf muscles work together to help you walk or run.”

“And the tissues in my biceps help me wave my hand,” said Mike, waving his hand from side to side.

“That’s not all,” said Mike’s mom. “Various types of tissue in your body team up to make an organ. Organs perform specific functions in your body. For example, your heart is made of all four types of tissue. All of the tissues in your heart work together to pump blood through your body. The heart is one of five vital organs in humans. The other vital organs are the brain, kidneys, liver, and lungs.”

“So these organs are important in keeping me alive?” asked Mike.

“Yeah, and each organ performs its specific function because of the tissues that constitute it.”

“And the tissues are formed by cells! That is so cool!”

“That’s right. Just about everything a person does is thanks to the teams of cells that make up the tissues that make up the organs!”

“Wow! Unlike a football team competing against other teams, all the teams in the human body work together. That is amazing!” ====================================================================

PROJECT: Choose one or more activities below.

A. Make a model of the cell: Using food items or other items around your house, to make a model of a cell. Use the picture above for guidance. Be creative and try to use items that are the same shape as in the picture. Make sure to label your model so others know the parts of a cell.

To Get Credit: take a picture of your model and send it to your teacher. Or call your teacher during office hours (11:00-12:00) and describe your model.

B. Answer the questions: Answer the questions about the article. To Get Credit: Send the answers to your teacher for extra credit. Comprehension Questions

1. According to Mike’s mom, what is a cell?

a. a multicellular organism

b. the smallest unit of life

c. a type of tissue

d. a gel-like fluid

2. How does Mike’s mom compare the cell membrane and the nuclear membrane?

a. Both the cell membrane and nuclear membrane are coverings. b. Both the cell membrane and the nuclear membrane controls the cell’s activities.

c. Both the cell membrane and the nuclear membrane let out waste. d. Both the cell membrane and the nuclear membrane allow substances to enter the cell.

3. Read the following sentences from the text.

“But some creatures have just a single cell, like an amoeba. They are called unicellular

organisms. Other creatures, like us human beings, are collections of cells. These are called

multicellular organisms. Multicellular organisms can range in size from brown algae to

large animals like elephants and whales, which have trillions of cells."

What can be concluded about cells based on this information?

a. Unicellular organisms were once part of collections of cells.

b. Cells in multicellular organisms are stronger than unicellular organisms.

c. Cells can only support life if they are part of a multicellular organism.

d. Some cells can support life independently. Other cells support life collectively.


“A group of human cells band together and form a tissue. There are four main types of tissue in humans.

Connective tissues include blood or bones. These form connections between structures in the body.

Muscle tissues form muscles, which help us move. Nervous tissues are in the brain, spinal cord, and

nerves. This type of tissue helps to control many body activities. Epithelial tissues are tissues that line or

cover the different parts of the body. This type of tissue has various functions, such as protecting and

filtering.”

Based on this information, what can you conclude about tissues?

a. All tissues in the body have similar functions.

b. All tissues band together to form cells.

c. Each type of tissue has a different function.

d. Some tissues are more important than others.

5. What is this text mostly about?

a. how the parts of cells, tissues, and organs work together

b. the importance of mitochondria in the life of a human being

c. how tissues are made from groups of cells to serve different functions

d. the differences between unicellular and multicellular organisms


“That’s not all,” said Mike’s mom. “The organs in your body are made of various tissues. For example, your heart is made of all four types of tissue. All of the tissues in your heart work together to pump blood through your body. The heart is one of five vital organs in humans. The other vital organs are the brain, kidneys, liver, and lungs.”

“So these organs are important in keeping me alive?” asked Mike.

“Yeah, and each organ performs its specific function because of the tissues that constitute it.”

As used in this sentence, what does the word “constitute” most nearly mean?

a. take away from something

b. give something energy

c. make up the parts of something d. change in shape or size

7. Choose the answer that best completes the sentence below. __________ one type of tissue in the heart by itself cannot pump blood through the body, a

collection of the four types of tissue in the heart can work together as an organ to pump

blood.

a. For instance a. Thus b. Although c. Above all

8. What is an organ made of? (write your answer in complete sentences)

9. Why are all the different parts of the cell necessary? (write your answer in complete

sentences)

10. Explain how different parts of a human being work together in unison. Use evidence from the

text to support your answer.

C. Memorize the cell parts and their functions. Cut this chart into sections to make a memory game. Play the game with your family. To Get Credit: Take a picture of you playing the game and send to your teacher.



Science Grade 7

Week 2 Dates: April 27 – May 1

Human Body Systems

Learning Target: I can identify the human body systems


Read the articles about the different systems of the human body. Then do one or more of the activities after the articles.

Move Your Muscles!

By Sharon Guynup

Have you ever seen a movie or a TV show in which skeletons chase people? In reality, bones

don’t move all by themselves. In fact, bones don’t go anywhere at all without muscles.

When you bend your arm, you do it by using muscles. If you tighten the muscles in your arm, the

muscles make the bones and the rest of your arm move.

When you kick a ball, it’s the same thing. You tighten the muscles in your legs in order to move

your leg bones.

Can a skeleton chase you?

Here you can see some of the muscles in the muscular system. You can see that there are lots of

muscles in our bodies. There are about 650 muscles in the human body, in fact. About half of

your body’s weight comes from muscles!

Your body has about 650 muscles.

Muscles are important to us for many reasons. Can you think of some?

Muscles help us run and jump. They allow us to stand up and sit down. We use muscles when we

lift heavy objects. We also use them when we chew our food and when we smile. We even use

muscles when we breathe.

Muscles help us run.

Doctors divide muscles into two groups: voluntary muscles and involuntary muscles. Voluntary

muscles are muscles that you can make move and control. Involuntary muscles are muscles that

you can’t control. Involuntary muscles work without you even thinking about them. These

muscles work automatically.

The muscles that help you move your arms and legs are voluntary muscles. When you want to

pick up a box, you think about it and then tighten the muscles in your arms so you can lift the

box. You can also control the muscles in your legs when you want to make your body run or

jump.

You move the voluntary muscles in your legs to make your body run.

The muscles in your heart, however, are involuntary muscles. They keep your heart beating,

whether you are awake or asleep. You don’t have to think, “It’s time to beat again, heart!” These

muscles work automatically. There are involuntary muscles in your stomach, as well. Your

stomach muscles keep digesting your food without you reminding them to do the job.

A human stomach

Pumping Up the Heart (circulatory system)

Make a fist with one of your hands. Your fist is about the size of your heart.

Your heart beats between 85 and 90 times per minute. It pumps about 5 quarts of blood through

your body's 60,000 miles of blood vessels in one minute!

Even though the heart is a powerful muscle, many people's hearts don't work properly. A study

by Dr. Eric Rose indicates that a mechanical pump might help many of those patients.

Pump May Save Lives

Some people's heart muscles are so weak that the heart can't pump enough blood through the

body. That condition is called heart failure, and it can be deadly.

Leigh Haeger

The drawing shows some parts of the heart. Look up what each part does.

A report from the American Heart Association says about a little more than 5 million Americans

suffered from heart failure in 2013. Another report says that about 400,000 Americans develop it

each year.

Powerful drugs or a heart transplant can help many people who suffer from heart failure. But the

drugs don't always work, and heart transplants are risky.

For years, doctors have inserted a mechanical pump in the bodies of some patients who were

waiting for a heart transplant. The pump helped the heart do its job.

The study by Dr. Rose shows that the pump could be used permanently, instead of a heart

transplant. Pumps may be able to save the lives of up to 100,000 Americans a year, the study

says.

The VAD

The mechanical pump is known as a VAD, or ventricular assist device. VADs come in several

sizes and shapes. The smallest pump sizes can be implanted in a person's heart and belly. A tube

goes from the pump through the skin to a control unit placed on the person's waistline. The

control unit is connected to at least one battery pack that sits in a strap by the side of the person’s

body.

"This technology is going to make huge leaps in the next two to three years," heart surgeon

Robert Kormos predicted.

====================================================================

The Skeletal System

The skeletal system is made up of bones that give your body shape. The picture here shows what

the skeletal system looks like from the front. It also shows what it looks like from the side.

There are more than 200 bones in your body. Let's take a closer look at some of these bones.

The skeletal system seen from the side and from the front

The skull is at the top part of your body. Another word doctors use to refer to the skull is the

cranium. The skull, or cranium, has a very important job. It protects your brain.

You might think the skull is all one big bone. But that’s not the case. In fact, a human skull is a

set of 22 bones.

Human skull, or cranium

Rub the back of your neck. Can you feel the bone that’s right at the base of your neck? That’s

one of the bones in your spine, or spinal column. The spine is a chain of bones that runs down

through your neck and back. It runs from the base of the skull all the way down to your hips (or

pelvis).

The spinal column is made up of more than thirty smaller bones, stacked one on top of another.

These smaller bones are called vertebrae. The vertebrae protect a bundle of nerves called the

spinal cord. The spinal cord delivers nerve signals to and from the brain. Animals with spines, or

backbones, are called vertebrates. That’s because their spines are made up of vertebrae.

Human spinal column

If you tap on your chest, right in the middle, you can feel your breastbone. It’s also known as the

sternum.

If you tap a bit to the left or the right, you may be able to feel some of your ribs. The ribs protect

inner organs like the heart and lungs.

The rib bones look like the bars of a cage. That' why the set of rib bones are also called the "rib

cage."

Do you see the two large bones behind the rib cage? They are shaped like triangles. There’s one

on each side. These are your shoulder blades. The medical name for the shoulder blade is the

scapula.

Front view of the rib cage with scapulae (in back)

Your legs have bones in them, too. Two of these bones in your leg are called the tibia and the

fibula. These are the two bones in the lower part of your leg. The tibia is the larger of the two.

Rise Up (nervous system)

A treatment enabled a paralyzed man to

stand and take steps again.

It was an evening in July 2006. The Beavers, Oregon State University’s baseball team, had

recently won the College World Series. One of the team’s pitchers, Rob Summers, 20, was

retrieving his gym bag from his parked car when another car hit him. “The car then drove off,

leaving me there with no help,” says Summers.

Courtesy Rob Summers

The impact rendered Summers paraplegic—unable to move his lower body. His doctors told him

he’d never walk again—hard news for an active young man to hear.

“They told me that I had no hope,” says Summers. “My comment was, ‘You don’t know me very

well. I’m going to fight until I get well again.’”

Five years later, Summers regained the ability to stand and could take steps on a treadmill. His

recovery “remains unprecedented,” European researchers commented in the British medical

journal The Lancet. “We are entering a new era.”

Information Highway

The car that hit Summers seriously injured the lower part of his spinal cord—the column of

nervous tissue that runs through the backbone. It carries messages to and from the brain, the

body’s central organ. Radiating outward from the spinal cord is a web of motor neurons, which

govern movement. The damage done to Summers’s spinal cord stopped the brain’s messages

from reaching many of the motor neurons in his lower body, preventing him from standing or

walking.

Rob Summers after the accident that rendered him a paraplegic.

After the accident, Summers underwent two years of standard therapy—muscle massages,

lessons in how to use a wheelchair, and the like. Before then, little more could be done for

paraplegic patients. Summers had the good fortune, though, to be chosen for an experimental

research project. “Rob was an ideal candidate,” says one of the project’s researchers, Susan

Harkema, a professor of neurosurgery at the University of Louisville in Kentucky. “He was

young and in otherwise good health. He’s also a very determined, disciplined person —an

extraordinary young man.”

Summers stood with his father, Mike Summers.

In a four-and-a-half-hour operation, the research team implanted electrodes in Summers’s spinal

cord. The electrodes were then wired to a pulse generator that was implanted in his back. The

pulse generator is remotely controlled by a device outside the body.

Body’s Wiring

After the surgery, Harkema and her team began the treatment. They switched on the pulse

generator for two hours a day, electrically stimulating the nerves in his spinal cord. Nerves can

respond to electrical stimulation because the messages they carry take the form of electric

signals. Nerves are the body’s “wiring.”

On the third day of electrical stimulation, Summers was able to stand with assistance. “It was

unbelievable,” he says. “There was so much going through my head at that point. I was amazed;

I was in shock.”

By 2012, Summers could not only stand but also could walk slowly on a treadmill with the aid of

an assistant and a supporting harness. He was able move his hips, knees, ankles, and toes

voluntarily. The exercise had enabled his leg muscles to regain some of their former mass.

Sensory Signals

The brain does more than just control movement. It receives messages from all parts of the body.

Many of the messages come from the eyes, ears, nose, skin, and muscles. Those messages travel

by way of the sensory neurons. Summers’s spinal cord wasn’t totally damaged. It could still

receive limited sensory signals from the muscles in his lower body.

That residual feeling in his lower body might be what enabled the experimental treatment to

succeed, says Harkema. Sensory messages from the legs might have been traveling to

Summers’s electrically stimulated spinal cord, prompting it to send signals along the motor

neurons and make the legs move.

“Our big finding is that the spinal cord is as sophisticated as the brain,” says Harkema. “It has a

memory. When you walk, it remembers that you are on two legs or one. The spinal cord

basically takes information from the brain and then handles all the details. We didn’t know that

before.”

Patients who don’t have some physical sensation, as Summers does, may not be helped by the

treatment, says Harkema.

Body Control

Monitoring Summers’ Leg Movements Right: Neurosurgeon Susan

Harkema

Spinal cord damage can do more than impair limb function. Victims can lose bladder and bowel

control. Those functions are regulated by another part of the nervous system—the autonomic

nervous system—that radiates from the spinal column. It controls automatic processes in the

body, such as heart rate, blood pressure, sweating, and salivation. Summers has regained

function in his bladder and bowels. He also has been able to discontinue a variety of expensive

medications prescribed to alleviate pain and prevent heart disease.

“Now I can stand,” says Summers. “I’ve gotten my confidence back to just go out in public.” His

goal is to stand and walk completely normally. “I’m working toward that every day.”

Broken Cord

KRT/Newscom

The spinal cord carries nervous signals back and forth between the brain and the rest of the body.

An injury to it can cause a complete or partial loss of function depending on the severity of the

damage.

PROJECT: Complete one or both of the following activities

A. Draw a picure of the human body and include as many of the systems as you can.

B. COmpelte the cross word puzzle below. For those systems that you do not know.

Ask your family members to help you.

TO GET CREDIT: Take a picture of your human body picture with labels of the human body systems, or take a picture of your crossword puzzle and send to your teacher. Or call your teacher during office hours and tell them what the different systems do in the body.



Science Grade 7

Week 3 Dates: May 4 – May 8

Ecosystems

Learning Target: : I can identify how living and nonliving organisms work together to make an ecosystem.


Read the article about an Ecosystem. Then complete one or more of the activities listed at the end of the article.

Walking Around Town

It was a light, spring Sunday in Brooklyn, New York. Doug and his wife, Eve, were enjoying it with their copy of the Sunday New York Times newspaper, which they would pleasingly read section by section over a hearty breakfast of eggs, bacon, and, of course, some warm and soft New York City bagels.

Both Doug and Eve were hard‐working people, having to commute by subway throughout the week into different parts of their neighboring borough of Manhattan where both of their offices were located. Therefore, they usually took full advantage of their days off by lounging around their apartment, reading and watching television. This was especially true throughout the winter, when temperatures were too cold and the skies too cloudy in New York to make Doug and Eve leave their place if they did not absolutely have to. They could rest and recover from their long workweek indoors, away from the snow and chilly temperatures, just as well as they could outside, and probably even better so!

However, this was the first clear and relatively warm day of the year that Doug and Eve could go outside and enjoy wholeheartedly, without having to bundle up and pile on layers of clothing. Eve became anxious as the morning neared a close and the afternoon came upon them. She desperately wanted to go outside exploring and snap photos with her brand-new digital camera, which she had bought just the day before. She was worried that Doug would not be up for such a trip and he would give the excuse that he was too tired. Eve was also hoping she could coax Doug into becoming a little more enthusiastic about photography himself, so they could plan fun photo excursions together. After all, they lived in one of the five boroughs

of the city of New York, which ranks among one of the biggest cities in the world, and is overflowing with countless images worth capturing on a camera. Eve really loved photographing the city (though she would not take as many photos in the frigid winter time) and thought getting Doug into it too would give them an excuse to have some extra fun time together.

“Doug,” Eve began a little tenderly, and nervously. “How about we head into the city today?” (New Yorkers tend to refer to Manhattan as “the city,” even if they already are residents of the five boroughs because the island is really its epicenter.)

“What for?” asked Doug, sipping his juice with a puzzled look on his face.

Eve sighed. She was wishing for the conversation to go more smoothly.

“Well, I’d like to take some photos today. It’s beautiful outside! And I thought you’d like to come along,” she said.

Doug replied with a simple “Oh.” He folded his paper and put it down without much of an expression.

Eve didn’t know how to react to that. Then, Doug got up and left the room, making Eve wonder what in the world that meant. Did he want to go? Was he angry at the request?

“What are you doing?” she asked him, projecting her voice down the hall.

“I’ll be right there,” he said.

After a moment, Eve heard Doug’s footsteps reentering their little dining room. She looked up and saw him smiling, holding two cameras: her brand new one and the other one he had secretly bought for himself as well.

***

Doug and Eve left their apartment and began walking the pavement toward the subway stop they were very familiar with, looking forward to their day of photographing the wonderful sites of New York City. What they, like most New Yorkers and city dwellers around the world, probably did not even realize, is they were going to observe all the highlights while being part of a tremendous ecosystem.

People usually think of an ecosystem as something much more natural than a city with incredibly tall, manmade buildings on top of concrete that run parallel to streets with zipping vehicles spewing toxic carbon monoxide into the atmosphere. Typically, the ocean comes to mind as an example of an ecosystem, or the rain forests of South America, while the African deserts could be another. However, an ecosystem is simply defined as a community filled with

living and nonliving organisms that interact with each other within a particular environment. And an urban ecosystem is actually the one ecosystem that human beings are in fact most familiar with, while it is also arguably the only ecosystem in the world that is growing.

***

Like they usually do on Mondays through Fridays when travelling to and from their jobs, Doug and Eve decided to take a local subway line from their home in Brooklyn to the island of Manhattan to enjoy their Sunday.

New York City has a massive subway system that helps people get around. The trains travel above and below ground, over bridges and through tunnels. These electrical behemoths are vital parts of the city’s ecosystem for they, in effect, help people survive a bit easier than if the trains did not exist. Human beings are incredibly social creatures. In other words, they naturally desire communication and companionship with other people. The city’s subways allow that to happen with much more freedom and ease, not to mention the quicker pace that is possible compared to the alternatives of a horse‐and‐buggy or walking. Furthermore, the subways help individuals get to their jobs, allowing them and other people to be productive. Necessary goods, such as food and supplies, become more easily available to people with better transportation. Plus, important services like medical treatment and education can be more easily taken advantage of.

Both Doug and Eve took some last-minute photos of the incredible Manhattan skyline through the windows of the subway car before it headed underground, into a tunnel, and through the East River into the subterranean depths of Manhattan.

***

When Eve and Doug walked upstairs from the subway station onto a Manhattan sidewalk, the first thing they saw were tremendous skyscrapers standing thousands of feet high. The island of Manhattan is littered with hundreds of huge buildings that have become world famous for, not just their height, but also for their recognizable architecture and symbolism of mankind’s never-ending desire to create. Doug and Eve immediately reached for their cameras and started taking some photos of buildings like the Empire State Building, the Freedom Tower and the Chrysler Building.

Many of these skyscrapers are essentially incredibly large office spaces. Therefore, the buildings serve a vital function in the ecosystem in that they house many people throughout the day, while they are working on any number of projects that could help others. A large percentage of these buildings are also homes to restaurants and eateries where people not only enjoy plenty of available nourishing food, but commiserate with each other as well.

One of the drawbacks of so many skyscrapers is that it creates shade. This might sound like a positive, and it partially is because it gives people relief from the hot rays of the sun.

However, too little exposure to the sun is not a good thing either. The sun is blocked so often from New York residents by those buildings, that people are not getting enough Vitamin D into their bodies, because the sun’s rays help build the levels of Vitamin D.

Still, it is important to recognize that these buildings of Manhattan are, in some ways, as “natural” a thing as an anthill or a bird’s nest. First of all, human beings, who are undoubtedly a part of nature, have built them, and they have been built by raw materials taken up from the planet’s resources. Certainly, soil has been covered by concrete and iron, but there are plenty of places in nature where there is no rich soil, like Antarctica, for instance. The previously hilly island that had thousands of trees on it has simply been exchanged for an urban ecosystem containing different things that serve the same function as many others that are called more “natural.” In addition, skyscrapers still must be built with respect to many laws of nature. An elite architect along with a construction crew cannot simply erect a building that stretches to an infinite height. The effects of gravity, wind, and, yes, the density of soil still within the earth of Manhattan, must be considered in the planning and construction of a building.

***

Eve knew that if she was going to have a successful day of photography, she and her husband would have to take a trip to Central Park. Central Park is located in the middle of Manhattan and takes up quite a chunk of land. It includes a couple of ponds, hundreds of trees, large grassy areas, rocky parts, and trails for urban “hiking.” Many species of animals call Central Park home, too. For some of them, it may be the only place within New York City where they can actually survive.

Central Park was constructed because city planners knew that New Yorkers would need a getaway location, a place where they could reconnect with nature, or at least the parts of it that are more traditionally considered “natural.” It is still certainly the case that New Yorkers need this outlet, which explains why Central Park still exists today as the price of local real estate has only increased over the years. Parks like this one “soften” the urban experience, giving locals a place to relax and engage in important recreational activities. Many scientists note that, though cities are ecosystems and a growing part of nature, the loss of greenery is a severe problem that needs to change. The urban planners of today are becoming more sensitive to this by making sure to include parks, taking a page out of the books of those who helped create Central Park as they continue to build new cities and expand upon those that have already been founded.

Doug and Eve strolled around the park for quite a while. They took tons of photos, ate lunch together, and even rode the famous merry‐go‐round. They were truly taking advantage of the pleasures allowed by the existence of such an incredible and unique location.

***

When Doug and Eve left Central Park, they began to chat about all of the noise in the city and the overflowing garbage cans that were seemingly on every block. These are common complaints made by many about the urban ecosystem, and might be more noticeable just after leaving such a beautiful place. Though they are considered to be large negatives of urban life, it is nearly impossible for noise pollution and garbage to be avoided.

Noise pollution is a byproduct of the large population and all of the transportation needed to get them around. Without such transportation, humans would not be able to live, prosper, and interact as effectively. Many people would rather not think about the existence of bugs, rats and other organisms that can live off of garbage, but they too, are part of the ecosystem and would not be able to survive as easily in many other parts of the world.

***

Doug and Eve took the same subway back to their home in Brooklyn. Tired from a long day of walking around the city, they kicked off their shoes and sat on the couch in preparation for a nice movie viewing. The film was a documentary about living in the backwoods of Montana, enjoying life in a forest’s ecosystem. Doug and Eve thought about vacationing there, inspired by their afternoon in Central Park, wanting to be closer to some more nature. They didn’t even stop to think that they had both been active participants in an urban ecosystem, a particularly unique part of nature, over the course of the entire day.

PROJECT: Talk to your family about different communities that are around you. Are you part of a

community? Create an ecosystem and discuss the different members of it.

TO GET CREDIT: Take a picture of your ecosystem and send it to your teacher, or call your

teacher during office hours and describe your ecosystem.



Science Grade 7

Week 4 Dates: May 11 – May 15

Reproductive Health: Character Traits

Learning Target: I can identify genetic character traits and where I got them from.

Activities – Complete the following activities during the week to reach the learning target by Friday. If you choose, take a picture of your work and text or email the picture to your teacher.

According to Webster’s dictionary, “The passing on of physical or mental characteristics genetically from one generation to another.”

Inheritance of Traits

Everyone has traits: characteristics and qualities that make us who we are. We have physical traits, like brown hair, blue eyes, long legs, freckles and funny-looking toes. We also have personality, or character traits. Those include things like being great at telling jokes, compassion, intelligence, warmth, creativity.

Where do traits come from? It’s easy to spot certain physical traits that were passed down genetically from parents to offspring. Traits like red hair and knobby knees are inherited. What’s more complex, and, many would argue, more interesting, is to find the source of traits

that could have formed from individual reactions to a certain environment. Many traits exist in a gray area between these two extremes—inheritance and development.

One example is body type. This might seem like an easy one. People are genetically predisposed to their body type. But once diet becomes a factor, environment begins to play a major role in how the body develops. So body type is one example of a trait that is a combination of inheritance and interaction with an individual’s environment.

So many of our most defining traits have been learned, rather than inherited. For instance, if you’re really great at video games, it’s not because one or both of your parents passed down skills in some video game mastery gene. It’s because you practiced, played a lot of video games, and developed those skills yourself. If you have kids who turn out to be great at video games, it will be because they put in the hours, learned the skills, and memorized the moves necessary to master the video game.

Of course, there are ways our brains can form that are more advantageous to advanced video game playing. Say you were born with an extra-large, extra-powerful section of your brain that commands hand-eye coordination. That’s inherited. What you do with it, how you choose to develop that advantage, is up to you.

You can pierce your nose, get a tattoo, dye your hair, shave your head, get your kidneys removed, put on a silly hat—it doesn’t matter how much you alter your body during your lifetime. None of those things will translate into genetic material to be passed down to the next generation. Of course, if your children grow up in an environment with role models who are pierced, funny-hatted and covered in tattoos, that is very likely to affect how likely they are to get piercings, tattoos, and funny hats!

PROJECT: Talk to your families about the different characteristics that you have: What color eyes

do you have? Can you roll your tongue? Can your parents? Is your earlobe attached? Pinky shape - bent or straight? Do you or your family have a widow’s peak? Fold your arms - Is your right or left arm on top? What other characteristics do you have?

Make a chart of your characteristic traits. Interview family members to see if those traits were inherited or if they are skills you have learned.

TO GET CREDIT: Take a picture of your chart and send to your teacher. Or call your teacher during office hours (11:00-12:00) and tell them what traits your have and which parent or grandparent you got them from.



Science Grade 7

Week 5 Dates: May 18 -22

Genes and Heredity

Learning Target: I can discuss genes and heredity

Activities – Complete the following activities during the week to reach the learning target by Friday. If you choose, take a picture of your work and text or email the picture to your teacher.

Why Do Cave Fish Lose Their Eyes?

Carlsbad Caverns National Park

There are caves deep under the ground where the sun never shines. The only light that enters

these caves is from the headlamps of cave explorers. If you went inside of one of these caves and

turned off your headlamp, you would see nothing at all. There would be no shadows or shapes,

just blackness.

In some of these caves, there are organisms that live without light. They include salamanders,

crustaceans, and fishes. In fact, more than one hundred species of cave fishes live in darkness for

their whole lives. They depend on senses other than sight to hunt, eat, and reproduce. These

fishes have evolved, or developed over many generations, to live without light.

Many of these species of fishes are blind or nearly blind. Some of them don’t even have eyes.

Yet they all evolved from fishes that could see. Somehow, over millions of years, these fishes

both lost the ability to see and gained the ability to live without sight.

How did that happen? How can evolution cause a species to lose a trait? It’s a mystery that

scientists have been trying to solve. Their search for an answer gives us a fascinating look at how

evolution works.

Regressive Evolution

We usually think of evolution as a process in which species gain new traits. But in cave fishes

we have an example of regressive evolution. Regressive means “going backward,” and

regressive evolution is a process in which species lose a trait. In this case, that trait is the ability

to see.

Blind cave fish, Mammoth Cave National Park, Kentucky

A common belief is that the ancestors of cave fishes went blind in their evolution because they

didn’t use their eyes. This idea might seem to make sense at first, but it has no basis in science.

Genes determine which traits are inherited. For example, the fact that you have five fingers on

each hand is because of the genes you inherited from your parents. However, if you lose a finger

in an accident, your children will still be born with five fingers on each hand. If you lift weights

and become a body builder, it doesn’t mean your children will be born with big muscles. In each

of these examples, your body has changed, but your genes haven’t.

Darwin Is Stumped

The fact that the ancestors of cave fishes didn’t use their eyes had no effect on their genes. Yet at

some point in the past, something clearly happened to their genes that stopped the development

of their eyes. This new condition passed on from parent to offspring. How can this sort of

regressive evolution be explained?

Even the scientist who established a modern understanding of evolution had trouble answering

this question. That scientist was Charles Darwin, who lived in the 19th century. At the time when

he was born, DNA hadn’t been discovered, so he didn’t know about genes or their role in the

inheritance of traits. But he understood that traits were inherited. He also knew that differences

within a species give some individuals an advantage over others. Animals with traits that make

them more successful at having offspring will pass on those traits to the following generations.

He called this process evolution by natural selection.

However, Darwin had trouble applying his theory of natural selection to the question of why

some cave fishes are blind. He could not explain how being blind gave those cave fishes an

advantage. And if being blind is not an advantage, then how did natural selection lead to a

species of blind cave fish? Darwin’s answer was that cave fishes lost their eyes because they

didn’t use them. His answer was a Lamarckian explanation. Today, scientists know that this

explanation is wrong.

Two Answers

Most of what we know now is based on the study of one species of cave fish. This species is the

Mexican tetra. Scientists after Darwin have come up with two possible explanations for

blindness in this cave fish. The explanations probably apply to other cave fishes as well.

The first hypothesis is that blindness gives the fish an evolutionary advantage. For example, it’s

possible that changes in the gene or genes that cause blindness also cause some other change in

the fish that is helpful. Scientists call changes in genes “mutations.” Scientists also have a word

for when the same mutation in one gene has more than one effect. That word is pleiotropy. To

support the first hypothesis, scientists would have to look for some advantage to the fish that is

connected with the same mutation that causes blindness.

The second hypothesis that could explain blindness in the cave fish also has to do with evolution.

Natural selection does not just reward success and preserve traits that give some animals an

advantage. It also gets rid of failures. To understand the second hypothesis, picture a lake where

there is sunlight. In this lake, a fish that is born blind would have trouble competing with other

fish that can see. It probably would not survive to have offspring. But a fish that is born blind in

the water of a dark cave would not be at a disadvantage compared to a fish that can see. That is

because eyes are useless in the dark. In such an environment, natural selection will not work to

get rid of the mutation for blindness. Over one to two million years, many more mutations

interfering with the development of eyes will occur and add up. After a while, the whole

population of fish in the cave will be blind. This is called the neutral mutation hypothesis. It is

based on the idea that the mutations that cause blindness have a neutral effect (an effect that is

neither good nor bad) on the survival of a fish living in a dark cave.

An Eye-Opening Experiment

A group of scientists set out to study the causes of blindness in the cave fish. They carried out an

experiment with two varieties of the same species of Mexican tetras. One variety of tetras lives

near the surface of water that gets sunlight. This variety can see. The other variety lives in water

in dark caves and is blind.

The scientists took a lens from the eye of a surface tetra embryo and put it into the eye of a cave

tetra embryo. The result was striking. The new lens in the cave tetra caused all of the tissues

around it to develop into a healthy eye. This experiment showed that even though the eye of the

tetra had stopped working, the genes involved in eye development still worked.

American Museum of Natural History

This result suggests that the neutral mutation hypothesis is wrong, because if blindness were

caused by many neutral mutations adding up over time, the new lens would not have resulted in

the development of a healthy eye. The scientists knew that there are many genes in charge of the

development of each part of an eye—such as the lens, the iris, and the retina. The scientists also

knew that each part of the eye develops on its own. However, the results of the experiment

showed that blindness in the cave tetra was not due to mutations in all those genes. Instead, it

suggested a small number of mutations in genetic “master switches.” These master switches are

genes that control the function of many other genes. In this case, some of the genes controlled by

the master switches were in charge of eye development. These “master switches” can deactivate

the eye genes so that the genes are still intact but not doing anything. Putting a healthy lens into

the cave tetra embryo seems to cause master switches to send a signal to the deactivated eye

genes. The eye genes are then “turned on,” and the cave tetra develops eyes. If the scientists

could find the master switches that made cave tetras blind, they could find out whether the same

switches had effects on other traits of the fish that do give it an evolutionary advantage for

surviving in caves.

The scientists did indeed find one of those genes. It is nicknamed Hedgehog or the Hh gene.

They discovered that this gene does more than cause blindness in cave tetras. When the fish

develops without eyes, the skull bones move into the empty eye sockets. When the bones move

into the eye sockets, the fish’s nose becomes bigger. In this way, it could be that the same master

switch (the Hh gene) that stops eye development in the fish is also responsible for improving its

sense of smell. An improved sense of smell would be an advantage for a fish that lives in the

dark.

As a result of this experiment and others, it now seems likely that blindness in cave tetras is in

part the result of pleiotropy. That is because the same mutation in one gene (the master switch)

has more than one effect (blindness and an improved sense of smell).

Evolution Works

Scientists are still studying cave fishes, and new discoveries are sure to be made. But it is already

clear where the answers to their questions will be found. The answers will be found in the basic

processes of evolution that are already well understood. With new tools that give scientists the

ability to map genes, find mutations, and understand the development of embryos, we are

increasing our understanding of how evolution works.

PROJECT:

Comprehension Questions

1. What ability have many cave fishes lost?

a. the ability to swim

b. the ability to smell

c. the ability to see

d. the ability to hear

2. To organize this text, the author divides it into sections with subheadings. What is described in the

section with the subheading "Two Answers"?

a. answers scientists have come up with about why some species of cave fishes are blind

b. answers scientists have come up with about why some caves receive no light from the sun

c. answers scientists have come up with about why some crustaceans have evolved to live without light

d. answers scientists have come up with about why regressive evolution occurs in salamanders

3. People's genes determine which traits they inherit. What information in the article supports this

statement?

a. "How did that happen? How can evolution cause a species to lose a trait? It’s a mystery that evolutionary scientists have been struggling to unravel. The search for an answer gives us a fascinating look at how evolution works."

b. "We usually think of evolution as a process in which species acquire new traits. But in cave fishes we have an example of regressive evolution, a process in which species lose a trait—in this case, the ability to see."

c. "...you have five fingers on each hand because of the genes you got from your parents. However, if you have an accident and lose a finger, your children will still be born with five fingers on each hand. If you lift weights and become a body builder, it doesn’t mean your children will be born with bulging biceps. In each case, your genes haven’t changed—even though your body has."

d. "The scientists knew that there are many genes responsible for the development of each part of an eye (for example, the retina, iris, cornea and lens). Each part develops independently. The results of the experiment showed that the genes for eye development in the Mexican tetra were all ready to work properly, given the correct signal."

4. Read these sentences from the text.

“The researchers did indeed find one of those genes. It is nicknamed Hedgehog or the Hh

gene. They discovered that the Hedgehog gene does more than cause blindness in cave

tetras—when the fish develops without eyes, the skull bones move into the empty eye

socket, which at the same time enlarges its nose. Unlike other vertebrates, fishes use their

nose only for smelling. It could be that the same control gene (Hh) that stops eye

development in the fish also enhances its sense of smell. An enhanced sense of smell would

be a definite advantage for a fish that lives in darkness.”

Based on this information, what can you conclude about the effect that the size of a cave

tetra's nose has on the cave tetra's sense of smell?

a. The smaller a cave tetra's nose is, the better the cave tetra's sense of smell will be. b. The bigger a cave tetra's nose is, the better the cave tetra's sense of smell will be. c. The size of a cave tetra's nose has no effect on the cave tetra's sense of smell. d. Any change in the size of a cave tetra's nose will make it more difficult for the cave tetra to

recognize smells.

5. What is the main idea of this text?

a. More than one hundred species of cave fishes live in constant darkness. b. If an animal is born with a trait that gives it an advantage over other individuals, it will be more

successful at having offspring, and its offspring will inherit the advantageous trait. c. The neutral mutation hypothesis is based on the fact that natural selection does not just reward

success but also weeds out failures. d. Many cave fishes are blind, and an experiment carried out by scientists suggests that blindness in

these fishes is the result of a mutation that also improves their sense of smell.

6. The title of this text is "Why Do Cave Fish Lose Their Eyes?" Why might the author have written the title

as a question?

a. to prepare readers for a discussion of possible answers to this question in the article b. to encourage readers to answer the question on their own before they read the article c. to criticize scientists for not having reached a definite answer about why cave fishes lose their eyes d. to praise scientists for the effort they have put into understanding the cause of blindness in cave

fishes

7. Read these sentences from the text.

“The fact that cave fishes don’t use their eyes has absolutely no effect on the DNA in their

chromosomes. They are blind because something happened to the genes that control the

development of their eyes. This change is passed on from parent to

offspring. That explains why a blind fish would have blind offspring. But it doesn’t explain

how a whole species of blind fish came to exist.”

How could you rewrite the last sentence without changing its meaning?

a. In particular, it doesn’t explain how a whole species of blind fish came to exist. b. Therefore, it doesn’t explain how a whole species of blind fish came to exist. c. For example, it doesn’t explain how a whole species of blind fish came to exist. d. However, it doesn’t explain how a whole species of blind fish came to exist.

8. Describe the first hypothesis that scientists have about blindness in the Mexican tetra.

Be sure to discuss pleiotropy in your answer. And use complete sentences.

9. One effect of the Hedgehog gene is to make cave tetras go blind. What is another effect it

might have? Use complete sentences.

10. As a result of the experiment scientists did with Mexican tetras, it seems likely that their first

hypothesis about blindness in the tetras is right. Explain how the result of the experiment

supports their first hypothesis. Support your answer with evidence from the text and images.

Use complete sentences.

B. Complete a word search or challenge a family member to see who could get more.

Allele Gamete Homozygous Metaphase

Autosomes Genes Hybrid Mutation

Chromosome Genetic Engineering Interface Molecular Genetics

Codominance Genotype Karyotype Phenotype

DNA Heredity Laws of Segregation Probability

Dominant Heterozygous Meiosis Punnett Square

Recessive Selective Breeding Sex Chromosmes Sexual Reproduction

TO GET CREDIT: Take a picture of your answers to the questions and/or the completed word search and send to your teacher. Or call our teacher during office hours and tell them about the reason why cave fish lose their eyes.

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Bernalillo Public Schools