The Journey Home Characteristics of many plants and animals vary greatly among the islands Hypothesis: Separate species may have arose from an original ancestor
Finches All had differentiated into 14 species different beaks specialized for a particular food source Conclusion – ancestral group of finches colonized islands – Absence of competitors allowed finches to gradually become specialized
People influenced Darwin Charles Lyell Malthus – populations can grow exponentially – the are limited by war, disease, or resources This led to Darwin’s idea that there’s a struggle for existence
Darwin’s Theory Humans can breed for certain traits – Dogs – Domestic plants Could also happen in nature – Over time this could produce new species
Darwin’s Theory Natural selection – organisms best suited for the environment reproduce more successfully – Survival of the fittest Over several generations organisms with favorable traits increase
1. Variation within a population 2. Variations are passed on
3. More offspring are produced than can survive
4. Organisms that survive have favorable variations (adaptations)
Modification by Natural Selection Fitness – genetic contribution to next generation Environment “selects” traits – Favorable traits depend on demands of env’t Greater fitness Better adapted Reproduce more
Summary of Darwin Natural Selection – organisms best adapted to the environment survive and reproduce the population is the unit of evolution – individuals do not evolve during their lifetimes
Theory of Evolution Evolution – change in the inherited traits of a population of organisms over time – NOT new species arising from pre-existing species Part but not all of evolution
What is natural selection? Agenda for Thursday Feb 19 th 1.Peppered moth lab 2.Finish theories coloring
Cheetahs are able to run faster than 60 miles per hour when chasing prey. How would a biologist explain how the ability to run fast evolved in cheetahs, assuming their ancestors could run only 20 mph?
A long time ago, some cheetahs were faster than the others The cheetahs that could run faster were able to catch their prey and were better able to survive The slow cheetahs died off, or weren’t able to reproduce as successfully The cheetahs that survived were the ones that could run faster
How does gene pool relate to variation? Agenda for Wednesday May 21 st 1.Finish theories notes
I can describe why the majority of the variation in a population is seen as a bell-shaped curve.
How did the heavy coat in polar bears evolve if their ancestors had thinner coats? 1. A long time ago, some polar bears had thicker fur than others 2. The thicker coat was favorable 3. The polar bears with thin coats died off. 4. The ones with thicker coats survived and reproduced.