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Ch. 6.3 Biological Evidence of Ch. 6.3 Biological Evidence of EvolutionEvolution

Ch. 6.3 Evidence of Evolution foldable:

• Create 6-tab foldable• Label front of tabs at top:

– Homologous structures– Analogous structures– Vestigial structuresVestigial structures– Developmental biology (embryology)– Comparing DNA sequences– Divergence

• On inside of tabs:– Description– How it supports theory of evolution

1. What evidence from living species supports the theory of evolution?

Focus Questions

2. How are Earth’s organisms related?

• As fossils were discovered, patterns emerged that showed many different species with similar body structures.

• Evidence suggests that species change over ti

What causes species to change over time?

time.

• Change over time = Evolution (to evolve)

• Biological evolution is the change over time in populations of related organisms.

• The fossil record is evidence that horses descended from organisms for which only fossils exist today

•The degree to which species are related depends on how closely in time they diverged, or split, from their common ancestor.

• Although the fossil record is incomplete, it contains many examples of fossil sequences showing close ancestral relationships.

• The fossil record indicates that different species of horses often overlapped with each other – not in a series of orderly steps.

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How do we know evolution happens?

http://www.pbs.org/wgbh/evolution/educators/course/session3/engage_a.html

• Comparative Anatomy – the study of similarities and differences among structures of living species.

• Homologous Structures – body parts are similar in structure, but different in function

Comparative Anatomy

The forelimbs of these species are different sizes, but their placement and structure suggest common ancestry.

Evidence: More similar structures = more related species (evolved from common ancestor)

Analogous structures: Body parts are similar in function, but

Comparative Anatomy

different in structure (not closely related)

(ex: bird wings vs. insect wings)

Evidence: Differences in structures = species are not related

What term refers to body parts of organisms that are similar in structure and position but different in function?

A. Camouflage

B. Mimicry

A. B. C. D.

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B. Mimicry

C. Analogous structures

D. Homologous structures

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Vestigial structures are body parts that have lost their original function through evolution.

Comparative Anatomy

Section 1 Change over Time

Evidence: shows relation to ancestors who used the part for a specific purpose

Which of the following is NOT evidence that whales evolved from mammals that once lived on land? 1 111

A. fossil discoveries that link whales to mammals

A. B. C. D.

B. the hip bones of whales

C. the fishlike shape of whales

D. the fact that whales are mammals

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Studying the development of embryos can also provide scientists with evidence that certain species are related.

Embryology – The science of the

Developmental Biology

development of embryos from fertilization to birth

Evidence: similarities in development of parts show relatedness

All vertebrate embryos exhibit pharyngeal pouches at a certain stage of their development.

In reptiles, birds, & humans, pharyngeal pouches develop into a gland in the neck – in fish, they form gills. (both glands & gills regulate calcium)

2. How are Earth’s organisms related?

g ( g g g )

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Rat Chicken Human http://www.pbs.org/wgbh/evolution/library/04/2/quicktime/l_042_02.html

What term refers to body parts that perform a similar function but differ in structure?

A. Analogous structures

B. Homologous structures

A. B. C. D.

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B. Homologous structures

C. Pharyngeal pouches

D. Vestigial pelvis

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• Molecular biology is the study of gene structure and function.

• Discoveries in molecular biology have confirmed and extended much of the data already collected about the theory

Molecular Biology

data already collected about the theory of evolution.

• Comparing DNA Sequences: Scientists compare the similarity of genes (DNA) & proteins to study the relatedness of living species.

Aligned DNA fragment and first chromosome banding patterns for man (Homo sapiens), chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla), and orangutan (Pongo pygmaeus).

Evidence: the more similar the DNA is, the more related the species

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Divergence: Using the rate of DNA mutations (“molecular clock”) to estimate when species changed

Molecular data indicate that whales and porpoises are

Molecular Biology

whales and porpoises are more closely related to hippopotamuses than they are to any other living species.

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Evidence: shows how closely related species are to each other

When was the last time Whales and Even-toed hoofed mammals shared a common ancestor?

0%

0%

0%

A. 35 mya

B. 50 mya

C 65 mya0%

C. 65 mya

D. 75 mya

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2 Views on the rate of natural selection:A. slowly and steadilyB. change occurs in short bursts after long

periods of stability.

• The fossil record is still incomplete, but new fossils are being discovered all the time.

• For example, the Tiktaalik fossil has both fish and amphibian features – linking the 2.

• Most evolution research is now done at the molecular level, but Darwin’s basic principles still hold true after 150+ years.