evolution & natural selection essential question: what evidence is there to support darwin’s...
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Evolution & Natural Selection
Essential Question: What evidence is there to support Darwin’s theory of evolution?
Evolution is how life changes over time, how new kinds of living things come from older ones. Charles Darwin’s theory of evolution by natural selection is accepted by biologists as the best scientific explanation for how life on Earth came to be as it is today.
1a. 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.
1b. 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.
1c. 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.
2a. 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?
http://www.youtube.com/watch?v=tqWciuuKn3c
Lungfish
Mudskippershttp://www.youtube.com/watch?v=aAz7iMcC8e0
Dragonfly with 2 ft. wingspan
Wooly Mammoth
2b. 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.
2c. EVIDENCE OF EVOLUTION: SIMILARITIES IN EMBRYOLOGY
• Early stages of many animals (e.g. birds, reptiles, mammals) are very similar, pointing toward common ancestry.
Vertebrate embryos at 3 weeks
2d. EVIDENCE OF EVOLUTION: SIMILARITIES IN DNA
• The more similar DNA is in different animals, the closer they seem to be related.• Similarities in DNA points to common ancestors.
Human DNA and chimpanzee DNA is 98% identical
2d. EVIDENCE OF EVOLUTION: SIMILARITIES IN DNA
• The more similar DNA is in different animals, the closer they seem to be related.• Similarities in DNA points to common ancestors.
• DNA same genetic code found in ALL living things
• The more similarities in DNA, the closer they seem to be related.
History of Life on Earth in 24 hrs…..
http://www.youtube.com/watch?v=H2_6cqa2cP4
3. SUMMARY OF DARWIN’S THEORY. a. Summarize the key points of Darwin’s theory of evolution by natural selection:
1. Offspring look different from parents. Sexual reproduction, meiosis, DNA mutations all 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.
3b. 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.
Questions?
Good afternoon! 1. Please get a computer and start logging in, and2. Take out these two assignments….
7,8,9
4,5
4. Explain how natural selection could affect a population of plants or animals in a water environment that is becoming more acidic.• Animals that can handle more acidity will survive and reproduce,
making babies that can handle acidity.• Animals that can’t handle more acidity will die, meaning they
don’t reproduce, meaning animals that can’t handle acidity will die out.
5. Genetic variability = more variety in offspring, more chances of survival if environment changes. Predict how a drier climate could affect genetic variability of a population in an ecosystem. Describe a reason for your prediction.
• Drier climate means animals that depend on wet climate would die off. Animals adapted for dry climate (e.g. scaly skin to keep moisture in) would survive and reproduce.
6. What is the role of genetic mutations in evolution by natural selection? Suppose the climate were to get much colder. Describe how a mutation could benefit a population of organisms. In your description, be sure to:
- Identify a change caused by a mutation that could benefit a population.- Describe how that change could benefit the population.
• A mutation could cause animals to have thicker fur.
• This could benefit the population by keeping them warmer when the climate gets colder.
7. What is a species? How can you tell if two different organisms are the same species?
• Species = group of organisms that can breed and produce fertile offspring (offspring that can reproduce).
• Check to see if DNA is close enough.• See if they can breed and make fertile offspring.
Are lions and tigers the same species? Ligers cannot reproduce and make more ligers.
Good afternoon!
Please get a computer and start logging on….
Make sure you take a computer that’s plugged in!
8. Flies and ants are very different from each other in many ways though they have many similar genes. How does evolution by natural selection explain this similarity in genes?
• Flies and ants could have evolved from common ancestor.• Flies could have evolved from ants that mutated to have wings.
9. How could scientists infer the degree of evolutionary relationship between flies and ants? In your description, be sure to:
- Identify two methods scientists can use.- Describe the evidence scientists can gather from each to infer an evolutionary relationship.
• Look at how similar their DNA is.• Look for similar body structures.• Look for similarities in embryos.• Look for fossils that are similar to both.
10. Niche = a particular “job” done by an animal or plant in an ecosystem.
Describe how filling a unique niche in the meadow ecosystem allows bees to survive and reproduce.
Bees help pollinate flowers. This helps the flowers reproduce and gives bees food to survive.
Forest Niches
Produce food, oxygen for animals
Produce CO2 for plants, control populations
Eat dead things, provide nutrients for soil
Today’s task: “Carbon Matters”, question 3
Testing tip• Copy words from the question into your answer to make
sure you’re answering the question.
• For example…..– Q: “Predict how a drier climate could affect
genetic variability of a population in an ecosystem. Describe a reason for your prediction.”
– A: “A drier climate could affect genetic variability of a population by…... because….”
When finished….1. Log off computers and put back in cart.2. Pick up copy of Cycles of Matter and do questions 1-6.
Natural Selection: Survival of the Smartest…..
Get a computer and….
1. Go to class website2. Under “Links”, type in “Evolution Review”
Lamarck vs. DarwinLamarck
Darwin
Video: Darwin and Cooperation
“I AM” 21:27-28:05
Religion vs. Science in the 1600’s
Questions?
