Evolution What is evolution EVOLUTION the process by

Evolution

What is evolution? EVOLUTION: the process by which modern organisms have descended from ancient organisms through genetic changes over generations.

Adaptations: what are they?

• Adaptation: An inherited characteristic that increases an organism’s chance of survival. Can be physical or behavioral. Polar bear fur Leaf bug body Giraffe neck

Examples of Adaptations

How do organisms get their adaptations? Genetic traits (Phenotypes)

How do new adaptations arise in a population? Genetic mutations

SELECTION: Artificial selection- Humans select beneficial traits (selective breeding) Example: dog and horse breeds, food crops

Darwin’s Theory of Natural Selection: Organisms with the most favorable traits survive and reproduce & pass their traits to their offspring. Ex: Peppered moth http: //www. youtube. com/watch? v=Ly. RA 807 dj. Lc Fitness: Ability to survive and reproduce; measured by # of offspring

Analyzing Data The illustrations that follow represent snapshots of rock pocket mouse populations. Each illustration shows the color variation at two different locations, A and B, at a particular moment in time over a period of several hundred years. Count the number of light and dark mice present at each location at each moment in time. Record your counts in the data table.

What does the data show?

Rock Pocket Mouse 10 min http: //www. hhmi. org/biointeractive/making-fittest-natural-selection-and- adaptation Click on image to view video clip

Answer these questions on your paper: How does the rock pocket mouse illustrate natural selection? How did the variations in the rock pocket mice come about?

Darwin’s Theory of Natural Selection Divided into 6 parts: 1. Organisms produce more offspring than can survive • Organisms can die from many causes (disease, starvation, and predation, etc) • The environment can not support every organism that is born Example: 100 beetles can produce enough beetles to equal to the weight of the earth in only 82 weeks.

Darwin’s Theory of Natural Selection Divided into 6 parts. 2. There is a “Struggle for Existence” • Members of each species must compete for limited resources (food, living spaces, etc. )

Darwin’s Theory of Natural Selection Divided into 6 parts: 3. Populations are made of individual organisms that differ in their traits • Not all the individuals of a population have the same traits • Adaptation – Inheritable physical traits that aid in an organism’s survival Examples: whales and dolphins have nostrils on top of head, lost hind limbs, hairless sleek body to reduce resistance

Darwin’s Theory of Natural Selection Divided into 6 parts: 4. Individuals that are best suited for their environment survive and reproduce most successfully • Survival of the fittesti. Individuals that are not well suited to the environment die or leave few offspring ii. Individuals that are well suited to the environment pass these beneficial traits to their offspring

Darwin’s Theory of Natural Selection Divided into 6 parts: 5. Natural selection- organisms with the most favorable traits survive and reproduce and, over long periods of time, these helpful traits gradually appear in more and more of the offspring. • Artificial selection- Selection by humans for breeding useful traits from natural variation among organisms (aka selective breeding) Examples: Food crops, dog breeds

Darwin’s Theory of Natural Selection Divided into 6 parts. 6. Descent with Modification-species alive today have descended, with changes, from species that lived in the past 1. All living things are related to one another. 2. Common descent: all living things were derived from one common ancestor

TAKE A MOMENT TO REVIEW YOUR NOTES & COMPLETE THE ASSESSMENT TO GAUGE YOUR UNDERSTANDING OF NATURAL SELECTION

1. Natural selection is sometimes described as “survival of the fittest. ” Which of the following most accurately measures an organism’s fitness? a. How strong the organism is when up against others of the same species. b. The mutation rate of the organism. c. How many fertile offspring it produces. d. The organism’s ability to withstand environmental extremes.

2. What does natural selection act on? A. Phenotype B. Genotype 3. Is it better to have a population with organisms that have all the same characteristics or with variety? Explain.

4. What does a biologist mean when stating that a particular organism is better adapted to its environment than another of that species? 5. What is meant by evolution? 6. How do genetic mutations impact evolution?