Evolution

Evolution

Charles Darwin

• 1700’s- Natural Theology dominated the time which said adaptations of organisms was evidence that the “creator” had designed every species (specifically created) for a particular purpose for a particular environment.

• *BIG DIFFERENCE BETWEEN EVOLUTION VS. CREATIONISM

• -Idea that all species were created at same time says they would all appear in rocks of same age but this in contrast to what paleontologists observe because some species appear than disappear in different rock layers.

• Jean Baptiste Lamarck- (1744-1829)• -published theory of evolution in 1809

(year Darwin was born)• -was in charge of invertebrate collection

at Natural History Museum in Paris• -saw many ladders of life that species

could move up (toward greater complexity)• -Evolution-according to Lamark was

toward greater complexity

• Lamarck’s Mechanism for Evolution• 1. Use/Disuse• Parts used= larger/stronger• Parts not used= deteriorate (waste away)• 2. Acquired Characteristics- modifications acquired during lifetime can be passed to offspring (ex. Long giraffe neck)• -NO EVIDENCE YET THAT GENES ARE

CHANGED BY THIS

Lamarck’s theory of acquired characteristics

• Charles Darwin-(1809-1882) born in Shrewsbury, England

• -read nature books- liked to fish, hunt, & collect insects as a boy

• -Charles earned his B.A. in 1831 & went w/ Captain Robert Fitzroy to sail on HMS Beagle

• -goal of the voyage chart poorly known stretches of the South American coastline

Voyage of HMS Beagle

• -Darwin spent most of his time collecting diverse/exotic species

• -Darwin noticed plants/animals had different characteristics than those in Europe

• *PUZZLING- Galapagos Islands- 900 Km west of South America but he saw animal species on Gal. that weren’t found in other parts of the world

• ex. Finches- 13 types collected; very similar but differed most in beaks adapted for special diet• -large ground finch- large beak for cracking seeds• -small tree finch- beak used to grasp insects

Darwin’s finches

• Darwin’s Findings• Origin of new species• Adaptation to environment • *Finch results- Darwin believed that if 1

species is separated by a geological barrier they could become dissimilar to be called different species

Closely related

• Darwin’s evidence for evolution• 1. Biogeography- islands species of plants/animals that are native to island but are closely related to mainland species• 2. Fossils- Bacteria prokaryotes are earliest known fossils so they should precede all eukaryotes• *Fossils do show this order (prokaryotes eukaryotes)• ex. Vertebrate record• fossil fishes amphibians reptiles mammals birds

• Darwin’s Beliefs about Evolution• 1. Struggle to Survive• 2. Individuals who inherit characteristics that best fit the env. will leave more offspring than less-fit individuals

• Evolution- change in populations over time• Charles Darwin- (1809-1882)• -published On the Origin of Species (1859)

which had 2 points:• All species evolve from ancestors• Mechanism for evolution natural

selection

• Evolution according to Darwin• *Natural Selection- mechanism for change in

populations• 1. Organisms produce more offspring than can survive ex. Fish lay millions of eggs• 2. In any population, individuals have variations ex. Fish differ in size, shape, color, speed, etc.

Evolution according to Darwin• 3. Individuals with certain useful variations such as speed are more likely to survive in their env. passing those variations on to the next generation• 4. Overtime, offspring w/ certain variations (adaptations) make up most of the population, & may look entirely different from their ancestors• *Modern Biologists-define evolution as a “change in a gene

pool (gene frequency) of a population over time”• SO, THE SMALLEST UNIT THAT CAN EVOLVE IS A

POPULATION!!

Natural SelectionThis diagram shows the natural selection process for a population with dark coloration.

• Adaptations/Structures which give evidence for evolution

• 1. Mimicry-structural adaptation that enables one species to resemble another species

• ex. Yellow jacket vs. syrphid fly• (harmful) (harmless-looks like yellow jacket)

• So, predators avoid eating both insects

• 2. Camouflage- adaptation that enables species to blend w/ their surroundings• -survive to reproduce b/c can’t be found by predators

Flounder blending in with sea floor rocks

• 3. Homologous Structures- can be similar in arrangement, in function, or both

• -evidence that organisms evolved from a common ancestor• ex. Whale, crocodile, & bird forelimbs are similar

Homologous Structures

• 4. Analogous Structures- body parts of organisms that do not have a common ancestor but are similar in function

• ex. Wings of butterfly & wings of birds

• . Vestigial Structures- body structure that has no function in a present day organism but was probably useful to an ancestor

• ex. Ostrich- has reduced forelimbs & can’t fly (ancestors probably foraged for food on land & nested on ground so they got too large to fly

Vestigial Structures

• Embryology- embryo- earliest stage of growth & development

ex. Embryos of fish, reptiles, birds, mammals all look the same & suggest a common ancestor