Evolution and BiodiversityEvolution and Biodiversity

APESChapter 5Ms. Miller

APESChapter 5Ms. Miller

Key ConceptsKey Concepts

Origins of life Origins of life

Evolution and Evolutionary processes Evolution and Evolutionary processes

Ecological niches Ecological niches

Species formation Species formation

Species extinction Species extinction

Origins and Early Evolution of LifeOrigins and Early Evolution of Life

Chemical evolution—evolution on Earth before life (evolution of organic molecules and chemical reactions)

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

Biological evolution—evolution of living organisms from single cell to multicellular organisms

Fig. 5-2 p. 88Fig. 5-2 p. 88

Evolution and AdaptationEvolution and Adaptation

Microevolution—small genetic changes that occue in a population

Microevolution—small genetic changes that occue in a population

Macroevolution—long-term, large-scale evolutionary changes by which new species form and others go extinct

Macroevolution—long-term, large-scale evolutionary changes by which new species form and others go extinct

Gene pool—collection of genes or genetic resources potentially available to a population’s offspring

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

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—when individuals have genetic traits that increase their chance of survival and fitness

Natural SelectionNatural 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. 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

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 AdaptationEcological Niches and Adaptation

Fig. 5-4 p. 91Fig. 5-4 p. 91

Ecological niche Ecological niche

Habitat Habitat

Fundamental niche Fundamental niche

Realized niche Realized niche

Broad and Narrow NichesBroad 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

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: cockroachesRefer 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 BiodiversitySpeciation, Extinction, and Biodiversity

Speciation—process of forming two species from one Speciation—process of forming two species from one

Fig. 5-7 p. 94

Reproductive isolation—long-term geographic separation of members of a species

Geographic isolation—earth feature blocks interactions of a population thus forming new species

Allopatric Speciation: Parent population of a species is physically

separated and spatially isolated.

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.

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

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 reproduction2) 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.

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.

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

5) Mating occurs but offspring are not viablea) die young or before birthb) are sterile

5) Mating occurs but offspring are not viablea) die young or before birthb) are sterile

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

ExtinctionExtinction 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)

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 extinction—a significant rise in extinction rates above the background level; widespread event 25-70% of species wiped out

Adaptive radiation—periods of recovery after a mass extinction

Adaptive radiation—periods of recovery after a mass extinction

Mass depletion—when extinction rates are higher than normal but not high enough to classify as a mass extinction

Mass depletion—when extinction rates are higher than normal but not high enough to classify as a mass extinction

Human Impacts—human activities are decreasing the earth’s biodiversity and are leading towards a mass extinction

Human Impacts—human activities are decreasing the earth’s biodiversity and are leading towards a mass extinction

Human Impacts on EvolutionHuman 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

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