APES Chapter 5

evolution by artificial selection

selective breeding of domesticated plants and animals to produce offspring with desired genetic traits

evolution

A change in the genetic composition of a species over time

recombination

A combining of genes or characters different from what they were in the parents

species evenness

Abundance of individuals within each species contained in a community

genetically modified organisms

An organism whose genetic material has been altered through some genetic engineering technology or technique

phenotype

An organism's appearance or other detectable characteristics

microevolution

Change in gene frequencies between populations of a species over time

mass extinction

Event in which many types of living things become extinct at the same time

How does geographic isolation lead to reproductive isolation?

If individuals cannot move between the populations, then over time, the two geographically isolated populations will continue to become more and more genetically distinct. Eventually, the two populations will be separated not only by geographic isolation, but also by reproductive isolation: they will become so different that even if the physical barrier were removed, they could no longer interbreed and produce viable offspring.

What is evolution, and what are the three main ways in which it occurs?

Evolution is the change in the genetic composition of a population over time. It occurs by artificial selection, by natural selection, and by random processes.

How does evolution lead to biodiversity?

Evolution produces more changes within a species, therefore increasing diversity.

macroevolution

Evolutionary change above the species level, including the appearance of major evolutionary developments, such as flight

How are human activities affecting extinction rates, and why is their impact a particular concern?

Human causes include habitat destruction, overharvesting, introductions of invasive species, climate change, and emerging diseases. Because much of the current environmental change caused by human activities is both dramatic and sudden, environmental scientists contend that many species may not be able to move or adapt in time to avoid extinction.

Why is it challenging to determine the number of species on Earth?

It is challenging because some species are active only at night or live in inaccessible locations.

realized niche

Part of a species fundamental niche that it actually uses, limited by competition

fossils

Preserved remains of once-living organisms

genetic engineering

Process of making changes in the DNA code of living organisms

range of tolerance

Range of chemical and physical conditions that must be maintained for populations of a particular species to stay alive and grow, develop, and function normally

geographic isolation

Separation of populations as a result of geographic change or migration to geographically isolated places

reproductive isolation

Separation of species or populations so that they cannot interbreed and produce fertile offspring

How does environmental change determine species distribution? When does it lead to extinction?

Species vary in their ability to move physically across the landscape as the environment changes, so species distribution is affected. It leads to extinction when the environmental change is so severe that the organism cannot survive there any longer.

What factors influence a species' chances of adapting successfully to a change in its environment?

The factors are rate of environmental change, genetic variation, population size, and generation time.

allopatric speciation

The formation of a new species as a result of an ancestral population's becoming isolated by a geographic barrier

sympatric speciation

The formation of new species in populations that live in the same geographic area

fundamental niche

The full potential range of the physical, chemical, and biological factors a species can use if there is no competition from other species

genetic drift

The gradual changes in gene frequencies in a population due to random events

species richness

The number of different species in a community

What is the difference between species richness and species evenness? Why are they both important measures?

The number of species in a given area, such as a pond, the canopy of a tree, or a plot of grassland, is known as species richness. However, species evenness tells us whether a particular ecosystem is numerically dominated by one species or whether all of its species have similar abundances. They are both important measures because they reflect biodiversity.

How do fundamental niches and realized niches differ?

The suite of ideal conditions is termed the fundamental niche of the species. However, the addition of biotic factors more narrowly defines the parts of the fundamental niche that a species actually uses. The range of abiotic and biotic conditions under which a species actually lives is called its realized niche.

Ecosystem Diversity

The variety of ecosystems

Species diversity

The variety of species

Why are estimates of species diversity valuable to environmental scientists?

They are valuable because they can tell environmentalists how much diversity is in a given area and what animals dominate it.

Why is the pace of human-driven evolution faster than that of natural evolutionary processes?

Using genetic engineering techniques, scientists can now copy genes from a species with some desirable trait, such as rapid growth or disease resistance. However, natural evolution occurs very slowly.

How are artificial and natural selection similar? How are they different?

With artificial selection, organisms are produced that humans find pleasing. However, with natural selection, the environment determines which individuals survive and reproduce. They are similar because traits are assigned to organisms in both cases.

bottleneck effect

a reduction in the genetic diversity of a population caused by a reduction in its size

niche generalists

a species that can live under a wide range of abiotic or biotic conditions

niche specialists

a species that is specialized to live in a specific habitat or to feed on a small group of species

fitness

ability to survive and reproduce

genotype

complete set of genes in an individual

mutation

occasional mistake in the copying process produces these random changes

genes

physical locations on chromosomes within each cell of an organism

founder effect

random change in the gene pool that occurs in a small, isolated colony of a population

distribution

the areas in the world where a species actually lives

phylogenies

the branching patterns of evolutionary relationships

evolution by natural selection

the principle that, among the range of inherited trait variations, those that lead to increased reproduction and survival will most likely be passed on to succeeding generations

adaptations

traits that improve an individual's ability to survive and reproduce

genetic diversity

variety of genes