Evolution Biological changes over time

Vocabulary Species – a population of organisms that can produce healthy, fertile offspring. Adaptation – inherited trait that increases chance of survival. Niche – a specific habitat, and the role a population plays in it.

Variation – differences between individuals in a population. Speciation – evolution of one or more species from a common ancestor species. Fossils – preserved remains or imprints of ancient organisms

Artificial Selection Domestic animals - cats, dogs, livestock Agriculture - fruits, vegetables, flowers Breeding animals or plants with desired traits only.

FEMALE MALE 2n = 64 2n = 62 2n = 63

Jean-Baptiste Lamarck Organisms strive to improve themselves Use and disuse theory – body structures used most will develop more. Inheritance of acquired traits.

Charles Darwin Sailed around the world on the ship HMS Beagle Studied differences in animals and plants Developed theory of Natural Selection

Darwin’s Trip to the Galapagos Islands Observed the finches on the islands and noticed each had its own niche. There were 13 different species of finches, and each had adapted to its own niche. Concluded that adaptations had led to new species emerging.

Natural Selection Natural variations exist within species, and they can be inherited. Some of these variations are favorable. They increase the ability to survive. All offspring born cannot survive. Individuals that survive to reproduce have favorable traits.

Figure Gradualism model. Species descended from a common ancestor gradually diverge more and more in their morphology as they acquire unique adaptations. Time (a) Punctuated equilibrium model. A new species changes most as it buds from a parent species and then changes little for the rest of its existence. (b)

Rate of Evolution Gradualism – Evolution occurs at a very slow rate. Small genetic changes in populations over many generations. Punctuated Equilibrium – Populations remain stable for long periods of time, with brief periods of rapid genetic changes.

Types of Evolution Convergent evolution – different species develop similar adaptations in response to similar environments.

Convergent Evolution

Convergent evolution

Divergent evolution populations of the same species become isolated, and evolve different adaptations in response to the environment.

Divergent evolution

Coevolution – Species that interact closely often adapt to each other.

Coevolution

Adaptive Radiation Evolution of many differently adapted species from one common ancestor species. As populations separate and occupy new niches, they will evolve different adaptations. Examples: Galapagos finches.

Fig A–C (a) Directional selection shifts the overall makeup of the population by favoring variants at one extreme of the distribution. In this case, darker mice are favored because they live among dark rocks and a darker fur color conceals them from predators. (b) Disruptive selection favors variants at both ends of the distribution. These mice have colonized a patchy habitat made up of light and dark rocks, with the result that mice of an intermediate color are at a disadvantage. (c) Stabilizing selection removes extreme variants from the population and preserves intermediate types. If the environment consists of rocks of an intermediate color, both light and dark mice will be selected against. Phenotypes (fur color) Original population Original population Evolved population Frequency of individuals

Directional selection – change in genetic frequencies in response to specific environmental changes. An existing adaptation may no longer be beneficial. A new adaptation may become more dominant with time.

Peppered moth – Directional Selection

Disruptive Selection – Selection that favors the extremes, selecting against what were the most common variations

Stabilizing Selection

Homologous Structures Traits that are similar in different species because they shared a common ancestor.

Analogous Structures Structures that are similar in function but different in structure. Species evolved independently of each other.

Vestigial structures Inherited structures that are not used by organisms. Indicates that ancestors once used them. Examples: pythons, some whales have hip bones, appendix in humans.

Reproductive Isolation Prezygotic Isolation Before Mating Habitat and Geographic Isolation Temporal Isolation Behavioral Isolation Mating Attempted Mechanical Isolation Gametic Isolation Postzygotic Isolation Mating and Fertiliation Hybrid inviability (reduced viability) Hybrid infertility (reduced fertility) Hybrid breakdown

Habitat Isolation

Geographic Isolation

Temporal Isolation

Behavioral isolation

Mechanical Isolation

Gametic Isolation Sex cells (gametes – egg and sperm) – can’t successfully pair up and make a zygote.

The End