differential reproduction
For natural selection to occur, a trait must be heritable, meaning that it can be passed from one generation to another. The trait must also lead to -----, which enables individuals with the trait to leave more offspring than other members of the populati
indicator species
Species that provide early warnings of damage to a community or an ecosystem
species diversity
An important characteristic of a community and the ecosystem to which it belongs is --- the number of different species it contains (species richness) combined with the relative abundance of individuals within each of those species (species evenness).
species richness
An important characteristic of a community and the ecosystem to which it belongs is its species diversity: the number of different species it contains---- combined with the relative abundance of individuals within each of those species (species evenness).
species evenness
An important characteristic of a community and the ecosystem to which it belongs is its species diversity: the number of different species it contains (species richness) combined with the relative abundance of individuals within each of those species
native species
are those species that normally live and thrive in a particular ecosystem.
adaptation, or adaptive trait
any heritable trait that enables an individual organism to survive through natural selection and to reproduce more than other individuals under prevailing environmental conditions.
background extinction
Throughout most of history, species have disappeared at a low rate
biological diversity, or biodiversity
the variety of the earth's species, the genes they contain, the ecosystems in which they live, and the ecosystem processes such as energy flow and nutrient cycling that sustain all life.
biological evolution
the process whereby earth's life changes over time through changes in the genes of populations.
ecological niche
Scientists describe the role that a species plays in its ecosystem as its ----, or simply niche (pronounced "nitch"). It is a species' way of life in a community and includes everything that affects its survival and reproduction, such as how much water an
endemic species
Species that are found in only one area are called ---- and are especially vulnerable to extinction.
fossils
Most of what we know of the earth's life history comes from ----: mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such items found in rocks.
foundation species
Another important type of species in some ecosystems is a -----, which plays a major role in shaping communities by creating and enhancing their habitats in ways that benefit other species.
generalist species
----- have broad niches. They can live in many different places, eat a variety of foods, and often tolerate a wide range of environmental conditions.
geographic isolation
occurs when different groups of the same population of a species become physically isolated from one another for long periods.
keystone species
A keystone is the wedge-shaped stone placed at the top of a stone archway. Remove this stone and the arch collapses. In some communities and ecosystems, ecologists hypothesize that certain species play a similar role. ----- have a large effect on the type
mass extinction
is a significant rise in extinction rates above the background level.
mutations
The first step in this process is the development of genetic variability in a population.This genetic variety occurs through mutations: random changes in the structure or number of DNA molecules in a cell that can be inherited by offspring.
natural selection
Darwin and Wallace concluded that these survival traits would become more prevalent in future populations of the species through a process called -----, which occurs when some individuals of a population have genetically based traits that enhance their ab
nonnative species
Other species that migrate into or are deliberately or accidentally introduced into an ecosystem are called ----, also referred to as invasive, alien, or exotic species.
reproductive isolation
mutation and change by natural selection operate independently in the gene pools of geographically isolated populations.
specialist species
In contrast, -----occupy narrow niches. They may be able to live in only one type of habitat, use one or a few types of food, or tolerate a narrow range of climatic and other environmental conditions.
speciation
Under certain circumstances, natural selection can lead to an entirely new species. In this process, called -----, two species arise from one.
extinction
Another process affecting the number and types of species on the earth is extinction, in which an entire species ceases to exist.