BIO 101: Chapter 9

community

All species that inhabit an area.

Late-Loss population

a population in which most individuals survive into adulthood; late-loss populations have a convex survivorship curve

Environmental resistance

when aspects of an environment limit population growth

Convex survivorship curve

Late-loss population

How are populations distributed in time?

Late-loss survivorship curve: younger individuals tend to survive, but survival drops with an organism's age Constant-loss survivorship: constant rate of survival at any age Early-loss survivorship: few young organisms survive, but the rate of survival increases as organisms get older

Exponential growth often occurs when

The birth rate exceeds the death rate for a single generation.

Natural increase

The difference between births and deaths in a population

What happens when a population exceeds carrying capacity?

The environment is damaged. One possible consequence is that there's extreme damage and the population dies out. Another option is that there's slightly less damage, but the carrying capacity is permanently lowered. Third option is that there's little damage, so resources recover and the population hovers around the original carrying capacity.

Random Distribution

distribution in which the location of members in a population is totally random, location of each individual is determined by chance

Density-dependent factors

factor that limits a population more as population density increases

Emigration

organisms leaving a population

Population cycles

fluctuations in population size in response to varying effects of limiting factors. Cyclical changes in the size of a population

Clumped Distribution

individuals are found in groups or patches within the habitat

A population size is likely to increase in size if

its reproductive rate is greater than replacement level fertility

Density-independent factors

limiting factor that affects all populations in similar ways, regardless of population size

Logistic Population Growth

population growth that levels off as population size approaches carrying capacity. "S" curve

Early-loss population

population where multiple offspring die early while some live

Growth rate

relative growth increase that's expressed in units of time

What is the carrying capacity sometimes symbolized as?

"K"

Survivorship table

A data table that groups organisms born at the same time and tracks them throughout their life span, recording how many continue to survive in each succeeding year (or other unit of time).

Carrying Capacity

Largest number of individuals of a population that an environment can support

Ecosystem

A biological community of interacting organisms and their physical environment.

Less developed country

A country that is at a relatively early stage in the process of economic development. Low income/education levels, high birth and death rates, haven't gone through demographic transition.

How have humans overcome environmental resistance?

Advancements in agriculture provided more food and increased the carrying capacity. Developing industrial and medical technology increase human's life span.

Biosphere

All living organisms and all nonliving aspects that support life on Earth

Population

All the members of one species in a particular area

Prey

An organism that is killed and eaten by another organism

Replacement Level Fertility (RLF)

Average amount of offspring that every female would have in order to keep a stable population

intraspecific competition

Competition among members of the same species

More developed country

Completed demographic transition. Has low birth and death rates

Concave survivorship curve

Early-loss population

How is population growth regulated?

Environmental resistance - when aspects of the environment limit population growth. Includes predators, availability of food/nutrients, and competition for resources. Usually regulates a population once the population reaches carrying capacity.

How has the human population been growing?

For the last 1,000 years, humans have been increasing exponentially. However, this growth can't continue permanently. At some point, density-dependent factors will impact the human population.

How does a population size change?

Four ways: 1) Increase in the population due to births 2) Decrease in population due to deaths 3) Increase due to immigration 4) Decrease due to emigration

Equation for population growth

G = r x n Population growth = growth rate x population size at the start of the time interval

Survivorship curve

Graph showing the number of survivors in different age groups for a particular species.

Would natural selection favor high or low biotic potential

High because when more organisms are born, there's more of a chance some of the organisms will have traits that can be selected for in an environment and organisms with these traits would be able to reproduce quickly and pass on their genes to more organisms

Factors that influence biotic potential

How frequently reproduction occurs, the age of first reproduction, how many offspring are generally produced each time the organism reproduces, the life span of reproduction for an organism, and the death rate under perfect conditions.

Demographic transition graph

In the pre-industrial stage, there were small, stable populations. During the transitional stage, food production and health care caused rapid growth - death rates lowered, birth rates stayed high. In the industrial stage, moving from farms to cities caused birth rates to fall. In post-industrial stage, both birth and death rates remain low, allowing the population to stabilize

Immigration

Movement of individuals into a population

Explain natural selection in terms of biotic potential and environmental resistance

Natural selection would likely prefer higher biotic potential because there are more organisms to have traits that could be selected for in a particular environment and organisms with those useful traits would be able to pass them along to more offspring in these conditions. Environmental resistance limits population growth. When these limits appear, some individuals in a population may have helpful traits that allow them to survive (fur that camouflages or warmer coats that keep them alive in colder months). These useful traits would be selected for and eventually passed down to future generations because the trait helped the organism fight environmental resistance and survive

Host

Organism that a parasite lives on/in and is harmed

Parasite

Organism that harms a host by living in or on it

Invasive Species

Organisms introduced into ecosystems where they didn't evolve, receive little resistance, and displace native species

Exponential growth

Population growth that is unhindered because of the abundance of resources for an ever-increasing population.

What would happen to a population without environmental resistance?

Population would grow exponentially forever. This would form a J-curve on a graph

Ecology

Scientific study of interactions among organisms and between organisms and their environment

K-selected species

Species that produce a few, often fairly large offspring but invest a great deal of time and energy to ensure that most of those offspring reach reproductive age. Usually mature slowly, live a longer life, and live in stable environments

r-selected species

Species that reproduce early in their life span and produce large numbers of usually small and short-lived offspring in a short period. They live in an unstable environment, don't usually reach carrying capacity, have a short life span, and mature quickly

Life history

Survivorship and reproductive features of a species Ex: when reproduction occurs and how many offspring are produced

Examples of density-independent factors

Temperature, Weather, Natural Disasters, Human Activity, Floods.

Uniform Distribution

Territorial organisms maintain a specific distance between each other

Biotic potential

The maximum rate that a certain population could increase

How are populations distributed in space

Three ways: 1) Clumped: individuals live in groups due to where resources are located 2) Uniform: individuals keep specific distance between each other (often due to territorial organisms) 3) Random: individuals are scattered by chance (rare)

When is there less momentum for future growth?

When there's fewer kids, there's less momentum for future growth and the population may become stable or shrink

When is there future population growth momentum

When there's more kids than reproducing adults, this forms momentum for future growth as the children eventually grow and enter their reproductive years.

S-Curve

a curve that depicts logistic growth; shape of an "S." The leveling off of a J-Curve exponential growth.

J-Curve

a growth curve that depicts exponential growth

Boom-and-Bust Cycle

a pattern of population growth in which exponential growth leads to a period when the population exceeds its carrying capacity, causing the population to decrease rapidly or crash

constant-loss population

a population characterized by a relatively constant death rate; constant-loss populations have a roughly linear survivorship curve

Predator

an animal that naturally preys on others.

demographic transition

change in a population from high birth and death rates to low birth and death rates. Stable population experiences rapid growth as death rates decline, then becomes stable as birth rates decline.

Interspecific Competition

competition between members of different species

Examples of density-dependent factors

competition, predation, parasitism, disease

Boom-and-bust populations may briefly

exceed the carrying capacity of their environment

Birth rate

the number of births in a year for every 1,000 people in a population

death rate

the number of deaths each year per 1,000 people

competition

the struggle between organisms to survive in a habitat with limited resources