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Cells and Systems

Grade 8 Science

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Topic 1 – Living Organisms

Take a moment to talk to the person next to you about all of the functions an organism needs to do to survive

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Functions and Structures

• All organisms need to perform certain functions to survive and they have certain structures to do it:– Energy: Organisms need to break down food

• we use our digestive system to do that physically

• at the cellular level, the mitochondria (an organelle) use the energy from sugars for us.

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– Environment: Organisms need to be able to adapt to their environment. Our environment is constantly changing, and many of our structures adapt to it.

– Growth: We need to grow and develop. We cannot reproduce until adulthood. Even single cells need to grow to a certain point before they can divide.

Functions and Structures

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– Wastes: Structures to get rid of the ‘leftovers’. We have two main systems for that – excretory, and digestive.

– Reproduction: Needed to allow the species to continue. If a species were to stop reproducing for one generation, they would go extinct.

Functions and Structures

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Define:

Organism

Cell

Life

Relate the three to one another in a sentence or two.

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• Levels of Organization

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• Levels of Organization– Starting with the largest level of organization: The

organism. • It is the entirety of the a living being.

– Each organism has a set of organ systems. • For example the digestive system

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• Levels of Organization– Each organ system is made up of several different

organs• The digestive system has the stomach.

– Each organ has several different tissues.• The stomach has muscle tissue, mucous layer tissue.

– Each tissue type is made up of one type of cell.• Muscle tissue is made up of all muscle cells.

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Microscopes

And Our Discovery of the Cell

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Your eye

• Open your textbook to page 103.– Read the first part ‘A World Too Small to See’

– Observe the 6 different circles. Our eyes can only differentiate between objects that are 0.100mm or bigger.

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• The typical cell is about 10µm, or 0.010mm– Our eyes would have to magnify 10 times more

than we see now to see them!

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• A bacteria cell is only about 0.5-2.0µm. Which is 0.0005-0.002mm, far smaller than our eyes could ever see without help.– Enter microscope

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Microscopes

• Anton van Leeuwenhoek (16232-1723) was the first to observe an organism made of only one cell. – He observed blood cells, pond water, and other

small accumulations of matter.

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Cells as a part of a living being

• Robert Hooke observed a network of box-like compartments in bark. He called them cellulae, which in Latin means ‘little rooms’.– Our word cell, comes

from this

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• The cell theory was developed, consisting of 2 parts1. All living things are composed of one or more cells2. Cells are the basic units of structure and function

in all organisms

• This came from the observation that larger organisms are made of cells at the microscopic level, and that each cell individually performs the 5 functions necessary for life.

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Parts of a microscope

• The microscope is made of several parts that work together to magnify an image.

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Parts of a MicroscopeFrom the top:• Eyepiece – Where

you look through• Tube – holds the

eyepiece and objective lens a precise distance from one another

• (Revolving) Nosepiece – Used to select the objective lens of your choice

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Parts of a Microscope• Objective Lens – Magnify the object. Usually 4X, 10X, or 40X magnification. Included with the 10X from the eyepiece lens, total magnification is 40X, 100X, or 400X its usual size.

• Arm – Connects the base and the tube

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Parts of a Microscope• Stage – The flat surface with a hole in the center to allow light to pass through and illuminate the specimen. Has clips to hold the specimen in place

• Condenser – Directs the light towards the specimen

• Diaphragm – Controls the amount of light reaching the specimen

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Parts of a Microscope• Illuminator – Used to

shine light at the specimen, sometimes more light makes picking out finer details easier

• Coarse Adjustment Knob – Used to bring the object into focus, used only with a low power lens

• Fine Adjustment Knob – Used to bring the object into focus with medium to high power lenses

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Parts of a Microscope• Base – Structural support

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The Cell and its Structures

Grade 8 Science

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Cells

• According to the cell theory, every organism is made up of cells. – They can either be unicellular (only one cell in an

organism)• Example: Bacteria, Amoeba, Algae

– They can also be multicellular (more than one cell makes up the organism)

• Example: Almost everything living you see! Humans, birds, most plants (except algae)

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Cells

• Every cell is made up of several organelles.– They are analogous (similar) to our organs in our

body. – Each organelle performs a certain function. The

collective work of all of the cell’s organelles is to perform the 5 functions of life.

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Animal Cell

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Plant Cell

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Organelles

• Cell Membrane – Permeable, Semi-Permeable, or Impermeable. Allows nutrients in/out and wastes out as needed.

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• Cytoplasm – Similar to our blood. It moves nutrients around the cell.

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Organelles

• Nucleus – Controls the cell’s activities through DNA, which direct the cell’s growth and reproduction

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• Vacuoles – Large organelles in the cytoplasm which store extra food, wastes, and other substances. Much bigger in in plant cells (provides rigidity).

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• Cell Wall – Only in plant cells. Thicker and rigid to support the plant

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• Chloroplasts – Only in plant cells. Where photosynthesis takes places. Uses sun energy to make carbohydrates (sugars) by using chlorophyll.

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Amoeba

http://www.youtube.com/watch?v=W6rnhiMxtKU

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Why cells?

• Why are larger organisms made up of billions of cells instead of one big cell?– Harder for bigger cells to move nutrients around

one another. Think of a human without blood, we would have to absorb everything from our environment!

– Many tiny individual cells work as a better transport system.

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Cell Size

• Come in a variety of sizes!• Most cells are approximately 10-50µm. Some

are as small as 1-5µm.

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Topic 4: Fluid Movement in Cells

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Diffusion Diffusion refers to the process by which molecules intermingle as a result of their kinetic energy of random motion. http://www.youtube.com/watch?v=M30PrtZDB8I&feature=related

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Consider two separated containers of gas A and B. The molecules of both gases are in constant motion and make numerous collisions with the separation.

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If the separation is removed, the gases will mix because of the random movement of their molecules. In time, a uniform mixture of A and B molecules will result.

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The tendency toward diffusion is very strong even at room temperature because of the high molecular velocities associated with particles.•All particles ‘jiggle’.

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Semi Permeable MembraneA semi-permeable membrane is a membrane which will allow the passage of certain molecules through it (by the process of diffusion), and not other molecules.

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The rate of passage depends on the pressure, concentration and temperature of the solvent on either side, as well as the permeability (how much it will let through) of the membrane to each type of molecule or solute.

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Osmosis Osmosis is the diffusion of particles across a semi-permeable membrane

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The semi-permeable membrane only allows the solvent particles to cross. The solvent particles diffuse until a balance between all the particles is reached.

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Osmosis is of great importance in biological processes where the solvent is water. The transport of water and other molecules across biological membranes is essential to many processes in living organisms. The energy which drives the process is usually discussed in terms of osmotic pressure.

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Vascular TissueVascular plants contain two main types of conduction tissue, the xylem and phloem. These two tissues extend from the leaves to the roots, and are vital conduits for water and nutrient transport. In a sense, they are to plants what veins and arteries are to animals.

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Vascular tissue consists of xylem and phloem. These two types of vessels run side-by-side, extending from roots to leaves. They provide channels for the transport of water and nutrients.

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Xylem TissueThe function of xylem tissue is to:• conduct water and dissolved minerals• Structural support

Tracheids Vessel Members

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Phloem CellsThe function of the phloem cells is to:• conduct food and other organic substances to different parts of the plant.

companion cells

seive-tube elements

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Transpiration - transfer of water from plants to the atmosphere.

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Plants pump the water up from the soil to deliver nutrients to their leaves. This pumping is driven by the evaporation of water through small pores called “stoma” (singular: Stomata), which are found on the undersides of leaves.

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• Transpiration accounts for approximately 10% of all evaporating water.

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Each stomata pore is bounded by two crescent shaped guard cells. Their opening and closing releases or retains the water within.

http://techalive.mtu.edu/meec/module01/Transpiration2.html

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Stomata

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Plant TranspirationThe evaporation produces what is known as the transpiration stream, a tension that draws water up from the roots through the xylem (water-carrying vessels in the stem).

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This replaces the water that is lost, and allows minerals absorbed from the soil to be transported through the xylem to the leaves. This is important because many plant cells need the minerals as nutrients.

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Grade 8 Science

Cell Specialization

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Orchestra Analogy

• You can think of the cells in your body as an orchestra. If you only had one type of cell or instrument in the orchestra, the orchestra would sound very plain. Orchestras are made up of many different types of instruments. Our bodies are made up of over 100 types of cells, this allows the music of our complexity to be incredibly intricate!

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Specialized Cells

• Different cells have different appearances and perform different jobs. They are ‘specialized’ for their job.

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Form Meets Function

• Cell shape is not just randomly decided. The shape of each cell type is designed in a way to assist with its function. This idea is called form meets function.Ex. Bone cells are strong for support, blood cells are shaped

to contain as much oxygen as possible

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Other Examples of Form Meets Function

• Nerve Cell – Elongated (long) and highly branched to allow for very quick transmissions of information

• Xylem cell – perforated to allow water (and the minerals dissolved in them) to freely travel through them.

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Why Specialized?

• Larger, more complex organisms can specialize parts of their body to carry out chunks of functions needed by all organisms. Remember:– Energy: Structures to break down food– Adapt to the Environment: Structures to survive

challenges– Reproduction: Needed to allow the species to

continue– Growth: Structures to mature– Get Rid of Wastes: Structures to get rid of the

‘leftovers’

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• Unicellular organisms must carry out all of those functions on their own! That severely limits them in several ways.– They cannot grow large because they don’t have a

system that is designed for transport, rather they simply allow diffusion to work.

– Must live in watery, food-rich environments because they cannot rely on moving around.

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Cell Organization

• Our bodies are organized from simpler structures, to more complex ones. – Cells are the simplest level of organization– Tissues are made up of a collection of the same

type of cells• Muscle tissue Nerve Tissue

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– Organs are made up of a collection of tissues

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Systems are made up of a collection of organs– Ex digestive system

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– Organisms are made up of a collection of systems

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Body Systems

Grade 8

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Digestive System

• http://www.youtube.com/watch?v=q3986Yfl5cU

• http://www.youtube.com/watch?v=OW2u6oYF9Iw

Food enters your body through your mouth and then passes to the stomach and intestines. It is broken down along the way into usable, soluble particles that can be used by different cells.

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Respiratory System and Circulatory System

• http://www.youtube.com/watch?v=bwXvqSqAgKc&eurl=http://video.google.ca/videosearch?q=circulatory+system+animation&www_google_domain=www.google.ca&hl=en&embiurl=http://i3.ytimg.com/vi/bwXvqSqAgKc/hqdefault.jpg&feature=player_embedded

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Respiratory System

• Breathing (the exchange of gases) move air in (inhalation) and out (expiration) of our bodies.

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Circulatory System

• Transports food and gases throughout our body.

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How the Respiratory and Circulatory System Connect

• The respiratory system exchanges oxygen and carbon dioxide, while the circulatory system transports those gases throughout the body.

• The interaction between these two systems happens in the tissues of the lungs.

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• Diffusion occurs between the alveoli (tissues of the respiratory system) and the capillaries (tissues of the circulatory system)

• Oxygen goes from the alveoli to the capillaries and carbon dioxide goes from the capillaries to the alveoli.

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How the Digestive and Circulatory Systems Connect

• The transfer of food particles, from the digestive system to the circulatory system, takes place at the inner lining of the small intestine, through millions of tiny, finger-like projections, called villi, which contain a network of capillaries.

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• The transfer of food particles is possible because of absorption. The villi absorb the food particles from the capillaries and then transport the nutrients to the cells, to be used as fuel.

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Excretory System

• http://www.youtube.com/watch?v=aQZaNXNroVY&feature=related– Up to 2:27

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Excretory System

• Filters waste materials from the blood. Glomerulus Kidney

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Sensory Awareness System

• Allows each of the systems of the body to respond to changing conditions and make adjustments in order to maintain a stable internal environment, allowing cells to function properly.

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• Quivering muscles generate heat.• 90% of heat loss is through the skin (most of the

rest is through the lungs)

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• Hairs on the skin stand on end when the tiny muscle cells near the surface contract, creating goose bumps.

• Fluffing body hair reduces hear loss by improving insulation in animals.

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Hypothalamus

• The nervous system helps to keep your body temperature stable by monitoring conditions outside, using temperature receptors in the skin. The information is then transmitted to the hypothalamus.

• Hypothalamus is the section of the brain which regulates body functions.

• The hypothalamus will decide what action needs to be taken.

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• Response to stimuli is coordinated by the nervous system (brain, spinal cord and nerves) and the endocrine system (glands that produce hormones).

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Nervous System

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Endocrine System

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• Diet, exercise, drugs, injury and disease can affect body systems and how they perform their functions.

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Blood – The Body’s Transportation System

• The blood vessels of the circulatory system form a complex network linking the outside environment with the internal environment of the body.

• The blood supplies all the living cells in the body with the nutrients they need to carry out their functions.

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Path of A Red Blood Cell. • http://www.youtube.com/watch?v=4HH3UXp

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About 8% of an adult’s body weight is blood.

Component % of blood Main function

Plasma 55% Carries nutrients, waste products, hormones and blood cells

Red blood cells 44% Carries oxygen (hemoglobin)

White blood cells >1% Defends the body against infection and disease

Platelets >1% Causes the blood to clot

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Blood Composition

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Plasma

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White Blood Cell

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A Healthy Circulatory System

• The heart circulates blood throughout the body by pumping it to where it can supply nutrients and remove wastes.

• Disorders include:– High blood pressure (hypertension)– Heart attacks (damage heart muscle)– Strokes (brain damage)http://www.youtube.com/watch?v=EQVEdFSlUGU

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Blood Pressure• Sphygmomanometer measures blood

pressure.• The blood is slowed and then listened to by a

doctor with a stethoscope.

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Blood Pressure indicates:

• The volume of blood• Heart Rate• Artery Size• Artery elasticity• Blood viscosity

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Disorders of the Circulatory System• Certain conditions place people at greater risk of

contracting a circulatory system disorder:– Smoking

• nicotine causes blood vessels to constrict increase HR increase BP

• Carbon monoxide competes with oxygen in the lungs, reducing the ability for blood to carry oxygen

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Healthy Digestive System• Food provides nutrients in the form of carbohydrates,

fats, proteins, vitamins, minerals and water. They provide energy and materials used for growth and development.

• Some foods cause poor health and promote disease– Refined sugar– Low fibre

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Disorders of Digestive System• High fibre diet is important to the colon to process

waste materials. • Low fibre can lead to colon cancer.• Long-term stress, smoking, excessive alcohol or

aspirin use can lead to a peptic ulcer.

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Healthy Respiratory System• Smoking, air pollution and industrial

by-products (coal dust) can lead to disorders of the respiratory system.

• http://www.youtube.com/watch?v=F0RuU2QHghM

• http://www.youtube.com/watch?v=lmZZlkrSu5o&feature=related

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Disorders of Respiratory System - Smoking• Cilia – hair-like projections in the lungs are used to

remove debris and particles. Poisons in cigarette smoke irritate the cells lining the lungs causing cells to produce more mucus.

• Lung cancer is caused by tar and smoke in cigarettes, which cause the lung cells to grow out of control.

http://www.youtube.com/watch?v=6NXaHGuRMsc&feature=relatedhttp://www.youtube.com/watch?v=6SN4xLqYTuE

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You and Your Body• Proper care means maintaining

healthy organs and organ systems. This can be accomplished with clean air and water, nutritious foods, exercise and sleep.

• Your immune system will work best when you are well fed, rested and healthy.