15-3 Outline:Evidence for Evolution

Essential Question: What evidence is there to support Darwin’s theory of evolution?

Characteristics of Living Things1. Living things are made of cells2. Living things reproduce3. Living things are based on a universal genetic code

(DNA)4. Living things grow and develop5. Living things obtain materials and energy6. Living things respond to their environment7. Living things maintain a stable internal environment8. Living things, as a group, change over time.

1. What is evolution?• How life changes over time, how new kinds of

living things come from older ones.

2. What is a theory? How is the scientific meaning of “theory” different from our every day use of the word?• Well-supported explanation for things we observe in

nature.• To non-scientists, theory means something “iffy.” To

scientists, it means something accepted as true; not “iffy”.• Plate tectonics is a theory, generally accepted as true.

3a. What did Darwin mean by “the struggle for existence?” Give an example in nature.

• Life is struggle to survive. Animals have to compete for food, shelter, mates, and avoid getting eaten by predators.

• Ex: Birds looking for nesting sites, polar bears looking for seals to eat.

3b. What does “survival of the fittest” mean? Give an example from nature.• Fitness = ability to survive and reproduce.• Organisms that are best adapted to their environment

survive and reproduce. • Ex: Deer that run fastest don’t get caught by wolves.

3c. What is an adaptation? Describe two adaptations a spider has for survival.

• Any inherited physical or behavioral characteristic that helps an organism survive.

• physical: fangs to inject venom in prey.• behavioral: web spinning to catch prey.

3d. What is the principle of “descent with modification?” Give an example from nature.

• Idea that living things look different from their ancestors because they changed as they adapted to different environments.

• Tigers, lions, cheetahs, panthers had common ancestors, e.g. sabertooth tiger.

4a. EVIDENCE OF EVOLUTION: FOSSIL RECORD

• Fossils show life has changed over time.

• Some fossils look very similar to animals alive today, some very different.

Archaeopteryx (150 mya)

What bird features do you see?What reptile features?

CoelocanthThought to have gone extinct 65 million years ago!

Lives in W. Pacific andIndian Oceans

What do you notice about its fins that isdifferent from most fish?

Dragonfly with 2 ft. wingspan

Wooly Mammoth

4b. EVIDENCE OF EVOLUTION: GEOGRAPHIC DISTRIBUTION OF LIVING SPECIES

• Animals that are same species but look different because they adapted to different environments, e.g. Galapagos finches.

4b. EVIDENCE OF EVOLUTION: GEOGRAPHIC DISTRIBUTION OF LIVING SPECIES

• Animals that are different species but look similar because they live in similar environments.

• American beaver, Australian wombat, South American capybara.

Beaver

Muskrat

Beaver & MuskratCoypu

CapybaraCoypu & Capybara

Beaver

Muskrat

Coypu

Capybara

4c. EVIDENCE OF EVOLUTION: HOMOLOGOUS BODY STRUCTURES

• Similar body parts in different animals (e.g. limbs of reptiles, birds, mammals) points to common ancestors. Changed as they adapted to different environments.

4d. EVIDENCE OF EVOLUTION: SIMILARITIES IN EMBRYOLOGY

• Early stages of many vertebrates (e.g. birds, reptiles, mammals) are very similar, pointing toward common ancestry.

Vertebrate embryos at 3 weeks

4e. EVIDENCE OF EVOLUTION: SIMILARITIES IN DNA

• DNA same genetic code found in ALL living things• The more similar DNA is in different animals, the closer they seem to be

related.• All human DNA 99.9% identical. Human and chimp DNA 98% identical.

Human and banana DNA 50% identical.

4e. EVIDENCE OF EVOLUTION: SIMILARITIES IN DNA

• DNA same genetic code found in ALL living things• The more similarities in DNA, the closer they seem to be

related.

4e. EVIDENCE OF EVOLUTION: SIMILARITIES IN DNA

• DNA same genetic code found in ALL living things• The more similarities in DNA, the closer they seem to be related• All human DNA 99.9% identical. Human and chimp DNA 98% identical.

Human and banana DNA 50% identical.

5. SUMMARY OF DARWIN’S THEORY. a. Summarize the key points of Darwin’s theory:

Natural Selection = the way evolution works1. Offspring look different from parents. Sexual

reproduction, meiosis, DNA mutations cause variation within species.

2. Organisms produce more offspring than can survive; have to compete for limited resources.

3. Individuals with characteristics that help them survive (e.g. camouflage colors) will live and reproduce, making offspring that have same characteristics.

4. Individuals that can’t compete don’t reproduce, don’t make more offspring.

5. This causes species as a group to change over time.

Lamarck vs. Darwin

5 b. Explain in terms of natural selection why dark colored beetles are common while brightly colored ones are not.

• Dark colored beetles blend in with their environment, harder for predators to see. More likely to survive and reproduce, making more dark-colored beetles.

• Bright colored ones easier for predators to see, more likely to get eaten. Won’t reproduce, meaning fewer brightly colored beetles.

EXTRA CREDIT (10 pts)Create a 1-2 page comic book or comic strip

illustrating key ideas from this chapter. Key ideas would include evidence for evolution, or how natural selection works. Should include colorful graphics as well as clear and well-worded explanations.

Peppered Moth Study