Evolution and Biodiversity APES Chapter 5 Ms. Miller

Key Concepts Origins of life Evolution and Evolutionary processes Ecological niches Species formation Species extinction

Origins and Early Evolution of Life Chemical evolution—evolution on Earth before life (evolution of organic molecules and chemical reactions) Biological evolution—evolution of living organisms from single cell to multicellular organisms Fig. 5-2 p. 88

Evolution and Adaptation Macroevolution—long-term, large-scale evolutionary changes by which new species form and others go extinct Microevolution—small genetic changes that occue in a population Gene pool—collection of genes or genetic resources potentially available to a population’s offspring Mutation—random changes in the structure or number of DNA molecules in a cell Natural selection—when individuals have genetic traits that increase their chance of survival and fitness

Natural Selection Natural selection is a relatively simple theory that involves five basic assumptions. The theory of natural selection can be better understood by identifying the basic principles on which it relies. Those principles, or assumptions, include: Struggle for existence - More individuals in a population are born each generation than will survive and reproduce.

Variation - Individuals within a population are variable Variation - Individuals within a population are variable. Some individuals have different characteristics than others.

Differential survival and reproduction - Individuals that have certain characteristics are better able to survive and reproduce than other individuals having different characteristics.

Inheritance - Some of the characteristics that influence an individual's survival and reproduction are heritable.

Time - Ample amounts of time are available to allow for change. It took thousands of generations to get to this

The result of natural selection is a change in gene frequencies within the population over time, that is individuals with more favorable characteristics will become more common in the population and individuals with less favorable characteristics will become less common.

Differential reproduction—selection that enables individuals to leave more offspring than other members of a population

Adaptive trait—any heritable trait that enables organisms to better survive and reproduce Anthropologist Nina Jablonski, Ph.D. theorizes that variations in human skin are adaptive traits that correlate closely to geography and the sun’s ultraviolet radiation, not race.

Coevolution—a back and forth adaptation duel between two interacting species in which one species gains a temporary advantage over the other The relationship between flowering plants and their pollinators can offer a classic examples of coevolutionary relationships. Flowering plants rely on pollinotors to transport pollen among indivudla plants and thus enable cross-pollination.

Ecological Niches and Adaptation Fundamental niche Habitat Realized niche Fig. 5-4 p. 91

Broad and Narrow Niches Generalist species—organisms with a broad niche that can live in many places, eat a variety of food and can tolerate wide range of environmental conditions Refer to Spotlight p. 92: cockroaches

Specialist species—organisms with a narrow niche that live in one type of habitat, use one or a few food sources and can tolerate a narrow range of climate and environmental conditions

Speciation, Extinction, and Biodiversity Speciation—process of forming two species from one Fig. 5-7 p. 94

Geographic isolation—earth feature blocks interactions of a population thus forming new species Reproductive isolation—long-term geographic separation of members of a species

Allopatric Speciation: Parent population of a species is physically separated and spatially isolated. Each population then takes on a slightly different traits and can, at times, cause such great differences that if the barrier is removed, they can’t interbreed.

Allopatric speciation of squirrels in the Grand Canyon . The canyon is a barrier to dispersal by small mammals, and as a consequence the isolated populations can diverge.

Parapatric Speciation: Population isn’t spatially segregated ; occurs more in plants. Spontaneous genetic abhorations which changes over time and diverge (mutations which survive and reproduce). Ex: number of chromosomes

Reproductive Isolating Mechanisms: work by preventing mating from occuring. The end result if EXTINCTION…not speciation 1) Ecological/Spatial Isolation: individuals are separated physically and unable to breed

2) Temporal Isolation: Species have different periods of sexual reproduction Example : Drosophila persimilis - breeds in early morning Drosophila pseudoobscura - breeds in the afternoon

3) Behavioral Isolating Mechanisms: Incompatible behaviors prevent mating from occuring. http://www.youtube.com/watch?v=cEh-zclVo44

4) Mechanical Isolation: Size differences, different reproductive tracts prevent mating from occuring.

5) Mating occurs but offspring are not viable 5) Mating occurs but offspring are not viable a) die young or before birth b) are sterile

Liger: male lion and female tiger Tigon: female lion and male tiger

Extinction Background extinction—when local conditions change and species disappear at a low rate (annual extinction rate of one to five species for each million species on earth) Mass extinction—a significant rise in extinction rates above the background level; widespread event 25-70% of species wiped out Mass depletion—when extinction rates are higher than normal but not high enough to classify as a mass extinction Adaptive radiation—periods of recovery after a mass extinction Human Impacts—human activities are decreasing the earth’s biodiversity and are leading towards a mass extinction

Human Impacts on Evolution Artificial Selection—process by which humans select desirable genes of a population (selective breeding); used in agriculture Genetic Engineering—(gene splicing)—techniques used to isolate, modify, multiply and recombine genes from different organisms Concerns about Genetic Engineering—unpredictable process and raises concerns in ethical, legal and environmental practices