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Principles of Evolution

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1 Principles of Evolution
Chapter 10 Principles of Evolution

2 Early scientists proposed ideas about evolution.
Evolution- is the change of a species over time where a descendant become different from their ancestors Species- is a group of organisms that can reproduce and have fertile offspring.

3 There were many important naturalists in the 18th century.
Linnaeus: classification system from kingdom to species Buffon: species shared ancestors rather than arising separately Erasmus Darwin: more-complex forms developed from less-complex forms Lamarck: environmental change leads to use or disuse of a structure Lamarck E. Darwin

4 Theories of geologic change set the stage for Darwin’s theory.
There were three theories of geologic change. Catastrophism- natural disasters such as floods and volcanic eruptions cause evolutionary changes in species or extinction Gradualism- slow change over a long period of time (gradual- slow) Uniformitarianism- states that geologic processes that shape the Earth are uniform through time (uniform- always stays the same)

5 Charles Darwin – p. 290. WHO. British naturalist WHAT
Charles Darwin – p WHO? British naturalist WHAT? 5 year voyage on the Beagle from England around the world WHERE? South America (Galapagos Islands) WHY? Study variation in life forms

6 Darwin Video

7 Darwin observed differences among island species.
Variation is a difference in a physical trait. Galápagos tortoises that live in areas with tall plants have long necks and legs. Galápagos finches that live in areas with hard-shelled nuts have strong beaks. An adaptation is a feature that allow an organism to better survive in its environment. Species are able to adapt to their environment.

8 Darwin observed fossil and geologic evidence supporting an ancient Earth.
Darwin found fossils of extinct animals that resemble modern animals. Darwin found fossil shells high up in the Andes mountains

9 Darwin noticed a lot of variation in domesticated plants and animals.
After his voyage, Darwin spent over 20 years conducting research on evolution Darwin noticed a lot of variation in domesticated plants and animals. Artificial selection is the process by which humans select traits through breeding. ex) faster horses, better fruiting plants neck feathers crop tail feathers

10 Theory of Natural Selection
Natural selection is a mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals. “survival of the fittest” Heritability is the ability of a trait to be passed down. There is a struggle for survival due to overpopulation and limited resources. Darwin proposed that adaptations arose over many generations.

11 Four main principals…. 1. Variation- heritable differences
2. Overproduction- having lots of offspring increases chance that some will survive ex) fish and reptile eggs 3. Adaptations- allow individuals to survive better than other individuals , more successful individual live longer and reproduce 4. Decent with modifications- more individuals will have more favorable traits in future generations

12 Interactive Natural Selection

13 Evidence of Evolution Fossil Records- Paleontology- the study of fossils or extinct organisms Geography Developmental Similarities Notochord Dorsal nerve cord Pharyngeal arches

14 4. Anatomy Homologous structures- similar in structure but different functions Analogous structures- similar function but are not similar in origin Ex) bat wing and insect wing Human hand Bat wing Mole foot

15 Structural patterns are clues to the history of a species.
Vestigial structures are remnants of organs or structures that had a function in an early ancestor.

16 Molecular and genetic evidence support fossil and anatomical evidence.
Two closely-related organisms will have similar DNA sequences

17 Embryonic Evidence

18 Fossil Evidence


20 Genetic variation is stored in a population’s gene pool.
Genetic variation in a population increases the chance that some individuals will survive. Genetic variation is stored in a population’s gene pool. made up of all alleles in a population allele combinations form when organisms have offspring

21 Sexual selection occurs when certain traits increase mating success.
Sexual selection occurs due to higher cost of reproduction for females. males produce many sperm continuously females are more limited in potential offspring each cycle

22 There are two types of sexual selection.
intrasexual selection: competition among males intersexual selection: males display certain traits to females

23 Geographic barriers can cause isolation.
called geographic isolation physical barriers divide population Temporal barriers can cause isolation. called temporal isolation timing of reproductive periods prevents mating

24 Evolution from natural selection isn’t random
Convergent evolution describes evolution toward similar traits in unrelated species.

25 Divergent evolution describes evolution toward different traits in closely related species
How do convergent and divergent evolution illustrate the directional nature of natural selection?

26 Species can become extinct
Extinction is the elimination of a species from Earth. occurs at roughly the same rate as speciation usually affects a few species in a small area caused by local changes in environment

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