Species Interactions, Ecological Succession, and Population Control

Species Interaction

- Interspecific competition
- Predation
- Parasitism
- Mutualism
- Commensalism
• All of these affect resource use and population size

- Food
- Shelter
- Space

Most Species Compete with One Another for
shared limited resources

Interspecific Competition

The most common type of interaction:
- When two species compete for the same resource, their niches overlap

Resource partitioning

• Occurs when competing species evolve specialized traits that allow them to use shared resources at different times, in different ways, or in different places

Predation

When an individual of one species feeds directly on another plant or animal species
- This has a strong effect on population size and other factors
- predator-prey relationship

Chemical warfare

- poisons, irritating (stinging), foul-smelling or bad tasting (can be poisonous)

Physical protection

- shells, thick bark, spines

Mimicry

- when a non-poisonous species looks like a species that is poisonous

Behavior strategies

- such as scaring off, puffing up, spreading wings, mimicking a predator, living in large groups (schools), or exhibiting warning coloration (indicating "eating me is risky")

Coevolution

- when populations of two different species interact over a long period of time, changes in the gene pool of one species can lead to changes in the gene pool of the other

Parasitism

occurs when one species feeds on the body of, or the energy used by another organism - usually by living on, or in the host

Mutualism

occurs when two species behave in ways that benefit both
- Providing each with food, shelter, protection, or some other resources

Commensalism

occurs when one species benefits from species interaction, and the other is not affected or harmed at all

Ecological succession

- The normal, gradual change in species composition in a given geographic area
- The species composition of an ecosystem or community can change in
- Natural geological restoration

Primary Ecological Succession

The gradual establishment of biotic communities in lifeless areas where there is no soil in a terrestrial ecosystem or no bottom sediment in an aquatic system - Takes hundreds to thousands of years

Secondary Ecological Succession

Occurs where communities or ecosystems have been disturbed, removed or destroyed, but retain some soil or bottom sediments
• Enriches biodiversity of communities and ecosystems by increasing species diversity and interaction among species

Living Systems

Are Sustained Through Constant Change
• Contain complex processes that interact to provide some degree of stability or sustainability

Two aspects of stability/sustainability

inertia (persistence) and resilience

Limits of population growth

- Limitations on resources
- Competition among species for these resources

population

is a group of interbreeding individuals of the same species, living together in the same geographic area

- Births/deaths
- Immigration (arrival of individuals from outside the population)
- Emigration (departure of individuals from the population)

tolerance

- its ability to survive under various physical and chemical environmental conditions

Population density

the number of individuals in a given geographic area

J-Curves

Some species reproduce and grow exponentially
- Members reproduce at an early age; many offspring in each generation; time between generations is short

Density-dependent factors

become more important as a population size increases
• Parasites and diseases spread more easily
• Sexually reproducing individuals can find mates more easily

Density-independent factors

• Drought and climate

Density-independent factors

Drought and famine

Environmental resistance

- The sum of all factors that limit the growth of a population

Carrying capacity

- The maximum population of a given species that a habitat can sustain indefinitely

S-curve

As population reach its carrying capacity, its J-curve becomes an ____ of fluctuating logistic growth.

Population Crash

When a population overshoots the carrying capacity, the population sharply declines
- Dieback

r-selected species

species that have a capacity for a high rate of population increase
- Have short life spans
- Have many, usually small offspring
- Do not provide much parental care/protection

Opportunists

reproduce rapidly under favorable environmental conditions
- Often occurs after a fire or clearing an area that opens up a new habitats or niches for invasion of a new species
- May crash after growth or when yet another species invades the area
- Go through irregular and unstable boom-and-bust cycles

k-selected species

- Reproduce later in life
- Have smaller numbers of offspring with longer life spans
- Typically develop inside their mothers and are born fairly large
- After birth, they mature slowly and are protected by one or both parents

do well in competitive conditions when population size nears carrying capacity

survivorship graph/curve

different species have different reproductive rates, they also have different life expectancies, illustrated by...
- Late loss
- Early loss
- Constant loss

technological, social, and cultural changes

The earth's carrying capacity for humans is expanding due to..