Chapter 7 Sections 2 and 3

Section 2 How Does Evolution Occur? In the early 1800’s scientists figured out that the Earth is older than previously thought Bizarre fossils were found Fossils were found in odd places Seashell fossils found on mountains

Charles Darwin Took the Beagle voyage in 1831 Had a degree in theology Dad wanted him to be a doctor but he couldn’t watch surgery, it made him sick

Charles Darwin Darwin was really interested in studying plants and animals On his 5 year Beagle voyage, he served as a naturalist, a scientist that studies nature He took samples and notes about the plants and animals he saw on the trip

Natural Selection Darwin’s observations became the foundation for evolution by the mechanism of natural selection Natural selection is also known as survival of the fittest Individuals with favorable traits will survive and pass those traits into the next generation

Beagle Voyage Darwin’s trip traveled to the Galapagos Islands, formed by volcanoes, off the coast of Ecuador in South America Darwin noticed that finches on the islands were similar but different than the birds on the mainland and other islands

Beagle Voyage

Darwin’s Finches Darwin noticed the finches on the islands had different beak shapes and ate different foods

Finches Darwin thought the finches on the islands originated from finches on the mainland Darwin figured the wind from a storm helped the birds fly to the new islands

Return to England Darwin used three sources to develop his evolution theory Farmers and breeders Geologists like Charles Lyell Thomas Malthus

Farmers and Breeders Selective breeding- traits are chosen that are favorable and only individuals with those traits are bred Example: Dogs There are over 150 breeds selective bred from the ancestral canine

In the wild For these types of changes to happen in the wild, it takes longer Variations in species is due to chance

Charles Lyell Darwin learned from Lyell that the earth was formed by natural processes over a long period of time Due to fossils and current species, Darwin had already thought changes in populations took a long time as well

Charles Lyell

Thomas Malthus Darwin learned humans and other animals can produce more offspring than the food supply will support Starvation and disease will kill off the weak and the strong will survive to reproduce the next generation

Thomas Malthus

Increase versus Food Availability Increase in human population Quantity Increase in food supply Time

Natural Selction In 1858, Darwin started to collaborate with Alfred Russel Wallace In 1859, Darwin published his research, The Origin of Species by Means of Natural Selection Darwin believed natural selection is how evolution occurs

Alfred Russel Wallace

Natural Selection Overproduction Genetic Variation Species produce more offspring than will survive to maturity Genetic Variation Individuals are different from each other slightly Some traits will increase chance of survival and reproductive success while other traits will decrease chances

Natural Selection Struggle to Survive Successful Reproduction Resources will vary in availability (food and water) Some will be killed while others survive Successful Reproduction Well adapted individuals will reproduce and produce offspring with similar “strong” traits while the weak will not live long enough to reproduce or only produce a few offspring

More Evidence 1930-40’s biologists combine genetic inheritance and Darwin’s theories to explain variance in population Variations are caused by mutations Mutation- change in genes

Section 3 Natural selection explains how a population changes over TIME. Generation time is the period between the birth of a generation and the birth of the next generation

Insect Resistance Some insects survive the farmer’s insecticides or poison and survive to produce offspring with the same genes until most of the population is adapted to resist the insecticide

Peppered Moths Peppered moths have 2 color variations, light and dark Before the industrial revolution the light moths blended into the trees better and were eaten less by birds and were more abundant in the population After the revolution, pollution made the trees darker and the darker moths were eaten less and more abundant

Peppered Moths

Formation of New Species Separation Part of the population gets separated Mountains, canyon, roads, river Adaptation Environment changes in one area Individuals adapt to that change Division Populations become so different over time they can no longer interbreed and become different species