The Theory of Evolution

Honors BiologyChapter 16

Build you biology muscle by exercising you QUADs!16.1 QUAD

What environmental factor determined the beak shape of the finches? Explain why.

16.1 The Theory of Evolution by Natural SelectionEvolution: Change in a population over time. Natural Selection: Process in which

organisms well suited to the environment survive and reproduce to a greater extent than organisms less suited to the environment.

Adaptation: An inherited trait that has become more common in a population because the trait provides a selective advantage

A. Darwin’s Voyage1. Charles Darwin: English scientist

a. In 1831, he set sail around the world on the ship Beagle. He spent five years collecting plants, animals, and fossils.

b. He found evidence that challenged the traditional belief that species are unchanging.

c. When he observed finches on the Galapagos Islands, he noticed both similarities and differences to finches on South America

Build you biology muscle by exercising you QUADs!16.2 QUAD

How did Malthus contribute to Darwin’s theory of Evolution by natural selection? Be as specific as possible.

16.2 Ideas that shaped Darwin's ThinkingA. Hutton (Geologist) 1780’s

1. Forces beneath the Earth’s surface can push rock layers and move them in the process

B. Lyell (Geologist) 1780’s1. laws of nature are constant over time 2. scientists must explain the past by looking at processes they can observe in the present

***Both agreed that Earth is extremely old & that the processes that changed the Earth in the past are still present today.

C. Lamarck1. Proposed that organisms can change over time by selectively using or not using body parts2. parents could pass these acquired traits down to their offspring causing changes in species over time

D. Malthus1. population size is limited by the resources available

E. Artificial Selection1. Humans breed plants and animals based on the traits that are desirable

16.3 Darwin makes his case1. Darwin’s Theory of Evolution by Natural

Selection: a. Inherited variation exists within the genes of every

population or species descent with modificationb. In a particular environment, some individuals are

better suited to survive and will have more offspring.

c. Over time, the traits that make certain individuals of a population able to survive and reproduce tend to spread in that population natural selection

d. In 1859, Darwin published the book called The Origin of Species.

16.4 Evidence of EvolutionA. The Fossil Record –

1. Fossils provide evidence for evolution.

a. Fossils provide a record of the Earth’s past life forms.

b. They provide “links” between living species and tell us when and where certain organisms lived.

Earliest Bat Fossil Icaronycteris sp.

B. Anatomy and Development1. Vestigial Structures: Structures that are no

longer used, but provide clues about their past, reduced in size

ex. the hind limbs of whales2. Homologous Structures: Structures that

share a common ancestry, but are modified in different species. Example: forelimbs of vertebrates.

3. Embryos (early stages in an organism’s development) are difficult to tell apart.

C. Biological Molecules1. Similarities between amino acids, proteins,

and nucleic acids help to identify species that may be closely related

2. The fewer the differences in them, the closer the relationship will be.

Vestigial Structure

Homologous Strucutre

Molecular Similarities

D. We must remember that not all features are inherited from a common ancestor.a. Convergent Evolution occurs when

similarities evolve in organisms that are not closely related to one another, but they live in similar habitats

Ex. Such as wings on birds and insects

b. The characters that arise through convergent evolution are called analogous characters.

Analogous Structures

E. Example of Evolution: The beaks of finches1. dry weather: beaks will be more-massive to

eat the large tough seeds. 2. wet weather: smaller beaks to gather the

small seeds that are available. The population of finches evolves to survive in the changing environment (See page 472, Fig 16-17).