Biological Evolution

Transcription

1 Biological Evolution

2 What is Evolution Evolution is descent with modification Microevolution = changes in gene (allele) frequency in a population from one generation to the next Macroevolution = descent of different species from a common ancestor over many generations

3 Evolution Explained NOT simply change over time Ex: Life cycle is NOT evolution MUST involve DESCENT through GENETIC INHERITANCE Change in a POPULATION over GENERATIONS of time Underlying Concepts: All organisms share a Common Ancestor Occurs through Natural Selection

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5 Natural Selection 1. Variation in traits: more than one allele for a trait; one allele may be more advantageous than another 2. Differential reproduction: NOT all individuals get to reproduce to their full potential 3. Heredity: adaptations are genetic 4. End result: more advantageous trait allows individuals to survive and produce more offspring

6 Natural Selection

7 Natural Selection

8 Natural Selection

9 Shift in Allele Frequency Mutations can produce new phenotypes that may or may not be beneficial to the organism If the new allele is beneficial, then those organisms will be more fit and therefore better able to reproduce. Over generations of time, this will cause the new allele to become more frequent in the population.

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13 Fitness Fitness = how good a particular genotype is at leaving offspring in the next generation compared to other genotypes FITNESS is INHERITED! Fitness will increase one or more of the following: Ability to Survive Find a Mate Produce Offspring Fitness is NOT necessarily strongest, fastest, or biggest. Ultimate Goal = transmit GENES to the next generation

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15 Sexual Selection Special case of natural selection Acts on an organism s ability to obtain &/or successfully copulate with a mate Organisms may go to extreme lengths for sex Peacock tail Elephant seals fight Fruit flies dance Some even die for it! (male praying mantis)

16 Artificial Selection Artificial Selection = people (NOT nature) select which organisms get to reproduce Farmers and breeders commonly cultivate crops using Selective Breeding

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18 Adaptation Adaptation = inherited characteristic in a population that increases fitness Adaptation Types Behavioral Biochemical Anatomical An adaptation is NOT ACQUIRED during an organism s lifetime

19 Lamarck = Acquired Traits (wrong) Giraffes needed longer necks so they grew longer necks through repeated use. THIS IS INCORRECT! Giraffes that INHERITED longer necks were better able to survive, so they passed those genes on to their offspring. Darwin = Inherited Variation & Natural Selection (correct)

20 Adaptation Functional = Produced by Natural Selection Heritable = MUST be able to be INHERITED (genetic trait) Adaptive = increases the fitness of an organism

21 Speciation Species is the biggest gene pool possible under natural conditions. If the organisms can breed and produce fertile offspring, they are the same species. German Sheppard + Chihuahua = puppy (fertile) Horse + Donkey = Mule (sterile hybrid) Horse & Donkey (NOT the same species) Speciation produces 2 or more separate species caused by: Geographic Isolation Reproductive Isolation

22 Speciation of Fruit Flies

23 A population of wild fruit flies lays eggs on rotting bananas

24 Disaster strikes: a hurricane washes the bananas and immature fruit flies out to sea. The bananas eventually wash up on the mainland. There are now 2 separate populations of fruit flies that cannot mate due to location.

25 Populations become different due to slightly different conditions on the island. This causes a shift in allele frequency in the island population because of selection pressures.

26 So we meet again: If another storm reintroduces the island fruit flies to the mainland fruit flies, they will not readily mate with each other due to differing courtship behaviors. The few that do mate produce inviable eggs because of genetic differences in the populations.

27 EVOLUTION DOES NOT WORK THIS WAY!!! What I NEED is a GOOD FUR COAT! Misconceptions Natural Selection does NOT produce perfection. An organism cannot adapt during its lifetime. It cannot try to change. That is NOT adaptation. Adaptations MUST be GENETIC! Natural Selection is NOT random: variations that aid survival and reproduction are more likely to become common in the population