Classwork: Evolution and Natural Selection

Group ____405_ __Name _____Valeria Elizondo A01194577 Vera Marcos A01194537

Introduction

Different individuals in a population have different characteristics. This is known as variation. Some of the variations in characteristics can be inherited by a parent’s offspring; and they are called heritable characteristics. Some characteristics make individuals better at surviving and reproducing than others. Fitness refers to the ability to survive and produce offspring that are capable of reproducing. The specific characteristics that contribute to fitness will differ in different environments.

A characteristic that increases an individual’s fitness is called an adaptation. Notice that biologists use the terms adaptation and fitness to have different meanings other than the common meanings of these words in everyday language. Living things that are well adapted to their environment survive and reproduce, while those that are not well adapted do not. An adaptation is considered any characteristic that increases fitness, which is the ability to survive and reproduce.

Heritable adaptive characteristics become more common in a population over many generations. This process is called evolution by natural selection. Evolution by natural selection is a gradual process that takes place over many, many generations. Evolution by natural selection results in changes in the frequency of characteristics and alleles or genes within a population, and not changes in an individual.

Which characteristics are adaptive and how a population evolves depends on what kind of environment the population is in. The same population will evolve differently if placed in a different environment. Organisms are not evolving to some pre-ordained “perfection” but are evolving to maximum fitness in a given environment.

Instuctions:

1. Study figures 1- 3 below, then answer the questions using these figures:

1

a) Is the population of mice found in figure 1 different that the population of mice found in figure 3? Explain why.

Yes, the white mice are disappearing and the grey mice are surviving with each generation because they camouflage.

b) What characteristic of the mice is an adaptation that increased their fitness?

Their grey color increased the fitness in an adaptation way.

2. Using your observation of figures 1-3, apply the scientific method to do the followinga) Write an investigation problem:b) State your hypothesis:c) Define the variables:

a. Independent: The color of miceb. Dependent: the number of micec. Controlled: The color of soil

3. The table below gives descriptions of four female mice that live on a beach that is mostly tan sand with scattered plants: Using the table above, answer the following questions:

Fur color black tan Tan and black cream

Age of death 2 months 8 months 4 months 2 months

# of pups produced by each female

0 11 3 0

Running speed 8 cm/sec. 6 cm/sec. 7 cm/sec. 5cm/sec

2

a) According to the definition of fitness, which mouse would biologists consider the fittest? Explain why.

The grey mice are the fittest, because they can camouflage in the soil and it makes them survive.

b) If the mouse´s fur color is generally similar to its mother´s color, what color fur would be most common among the pups?

Their most common color is the grey because of evolution by natural selection, that means that they survive longer with a grey color fur because they camouflage with the soil, and they are more probable to be born with their mother`s color that is more probable to be the survival color.

4. Below is a series of pictures representing changes in a population of cacti. Pictures 1 and 2 show what happened when a deer came to eat, picture 3 shows the cacti a few weeks later (notice the flowers on the right-hand cactus), and picture 4 shows the situation a few months later. Use these pictures to answer the following questions:

a) One characteristic that is necessary for natural selection to take place is variation in characteristics within the population. In picture 1, what is the main difference between the cactus on the left and the cactus on the right?

The difference is that one cactus has thorns and the other doesn’t.

3

b) Another characteristic necessary for natural selection to take place is differences in survival and reproduction fitness. Why would a deer be more likely to eat the cactus on the left than the cactus on the right?

One cactus has thorns and that make that cactus to survive more, because animals wouldn`t eat them because it will harm them, but the other cactus doesn’t has thorns so it makes it more a victim and in this example, victim of the deer.

c) What effect does the deer´s behavior have on the survival and reproduction of these two types of cactus?

The deer is eating the cactus without thorn so they are becoming more extinct, and the cactus with thorns are surviving and reproducing.

Another characteristic necessary for natural selection to take place is the heritability of characteristics from parent to offspring. The difference between the cacti is a heritable characteristic (see picture 4). Do you think that evolution by natural selection is occurring in this population? Explain why or why not.

Yes because of the evolution by natural selection so the ones that have thorns are being reproduced can survive more.

Evaluation

Criteria 3 2 1

Interpretation of figures 1-3

All questions related to the figures were answered correctly.

All questions related to the figures were answered, but some of them were not answered correctly.

All questions related to the figures were answered, but none of them were answered correctly.

The investigation problem,

The investigation problem,

4

Steps in the scientific method

The investigation problem, hypothesis and variables were all correct and were appropriate for the information given in the figures.

hypothesis and variables had some mistakes, but were appropriate for the information given in the figures.

hypothesis and variables had some mistakes, and were not appropriate for the information given in the figures.

Data interpretation Both questions pertaining to the data chart were answered correctly

One of the questions pertaining to the data chart was answered correctly.

None of the questions pertaining to the data chart were answered correctly.

Understanding the conditions necessary for natural selection to take place

All questions pertaining to natural selection were answered correctly.

Some of the questions pertaining to natural selection were answered correctly.

None of the questions pertaining to natural selection were answered correctly.

Team work The team members worked together to do the activity. They turned it in on time.

The team members worked together to do the activity. They didn´t turn it in on time.

The team members didn´t work together to do the activity. They didn´t turn it in on time.

5