Chapter 15The Theory of Evolution

Objectives 15.1

•SUMMARIZE Darwin’s theory of natural selection.

•EXPLAIN how the structural and physiological adaptations of organisms relate to natural selection.

•DISTINGUISH among the types of evidence of evolution.

Evolution• Theory that explains all the

changes that have formed life on earth from its beginning to common diversity

• Scientific theory NOT scientific fact

Based on a lot of info and experiments, some of which is debatable and some which is not-Earth’s age:

a) 4.6 billion years oldb) Estimate originally based on

only studies of the earths crust.c) Now also based on

radioactive dating.

Early Evolution Scientists

Lamarck (1800)- animals changed over time by passing on acquired traits

•Giraffes stretch necks to reach higher in trees during times of drought•Necks get longer•Children will acquire the long necks

Wallace (1840)- animals change by passing genetic traits that are best suited to the environment

•Giraffes have all different size necks due to the variations in genes.•During times of drought, the giraffe with the longer necks will survive and the giraffes with shorter necks will die•Long neck giraffes will mate•Long necked children will be produced

Early Evolution Scientists

Wallace

Charles Darwin• Began as a naturalist

on the HMS Beagle (an English ship).

• Collected specimens over his 5 year journey

• Small islands near the equator

• Species live here that live no where else in the world.

(Continued Charles Darwin)•Darwin (1840)-

theory the same as Wallace, but Darwin published the book called, “The Origin of Species”, so his name is more associated with the current evolutionary theory.

Darwin came up with 2 theories:

1) Decent with Modification: new forms of organisms descend from old forms but all species come from just a few original species.

2).Modification by Natural Selection: environment limits species by affecting its birth and death rates. Best suited to the environment will live and reproduce.

How do species evolve?

•Species evolve due to natural selection.

•Natural Selection- Process by which organisms that are best suited to the environment will survive and reproduce passing along the best traits for the environment “survival of the fittest”

-Fittest means the organisms is best suited to the environment

will survive and reproduce

Ex. 1) A type of deer are living in a temperate environment

2) There are all different thickness of furs on the deer. Some have thinner coats and some have thicker coats.

3) 2 separate groups of deer are formed due to geographical isolation (tidal wave, earthquake, etc). 4) 1 of the groups of deer migrates to a colder are and the other group moves to a hot environment.

5) Deer with thicker fur are more likely to survive in a cold environment, thin fur deer will survive in a hot environment. 6) Surviving deer will mate and pass their genes for their type of fur.

Why did deer have different thickness of fur to begin with?

•Variations of a trait, and this can be caused by mutations, crossing over, and genetic recombination•Variations are just different alleles for the same trait.

If a variation increases the organisms chance to survive and being able to reproduce than it’s called and adaptation.

Ex. -Opposable thumbs in

humans -Wings on birds - Elephant’s

large size and trunks

Traits that are good for one organism aren’t necessarily good for another.

Ex.Wings on an elephant No

flight Legs on a snake-

can’t slither in small places

Ball python- very muscular, unhinged jaw, large fangs, skin colorCock roach- exoskeleton, antenna, and ability to climbMillipede- a lot of legs, flexible, pieces of exoskeletonTarantula- fangs, 8 legs, hair (sensing), poison

Chameleon- Change colors, opposable claws, eyes, tongueScorpion- claws for protection, venom, and exoskeletonRing snake- colored for protectionBearded dragon- nails to climb

Traits that are good for one organism aren’t necessarily good for another.

Ex.Wings on an elephant No

flight Legs on a snake-

can’t slither in small places

Evidence of Evolution

• 1) Fossils: remains or traces of an organism that lived in the past

• a) Preserved hard parts-bones• b) Preserved in amber- insects in tree sap• c) Preserved in ice- wooly mammoth and man• d) Preserved in tar• e) Petrifaction- turned to stone• f) Imprints-footprints• g) Molds and cast• h) Burrows

• -Most fossils are formed when buried in fine sediments deposited by wind, water, or volcanoes

• -Fossils being formed with the exception, not the norm. The conditions have to be PERFECT.

2. Comparative Anatomy

• -Study of similarities and differences among living organisms

• -Homologous structures- similar structure but not necessarily similar function indicates common ancestor but different environments

• Ex. Forelimbs: almost identical in a variety of different animals

• -Analogous structures- structures similar in appearance and function but no near ancestor.

• Ex. Bird and insects have wings, evolved in similar environment but are different species.

• Vestigial structures- remnants of structures that were functional in an ancestral form.

• Ex. The human body ahs a bout 100 vestigial structures: coccyx, the appendix, wisdom teeth, the muscles that move your ears and nose

• Ex. Whales and pythons have hind leg bones

3. Comparative Embryology

• -Comparison of the patterns of development of the embryos of different types of organisms

• -The longer the organisms embryo resemble each other during development the closer related they are

• -Fish, birds, and humans all have gill slits, a two-chambered heart, and similar traits at one point during embryo development

4. Comparative Biochemistry

• -comparison of the DNA and similar protein molecules found in different species

• Ex. Man has 30,000 genes, 29, 550 are identical to a chimpanzee

• Ex. Hemoglobin (Blood Protein) is only different by one amino acid between gorillas and human, but is different by 67 between humans and frogs.

The Record of Life

• The sun with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do… galelio