Population and communites

Population?

A group of organisms of the same species living in the same area at the same time

Why is random sampling used to estimate population size?

• Gives practical and reliable estimates

• Unbiased and effective

Capture-mark-release-recapture?

A technique used to estimate population size by capturing, marking and releasing and recapturing individuals

Lincon index?

A mathematical formula used to estimate population sized based on marked individuals

Carrying capacity?

The maximum population size an environment can sustain indefinitely without degrading the habitat

What is negative feedback?

A process where changes trigger responses that counteract change

Density dependent factors?

Factors that increase with population density

Examples of density dependent factors?

• Predation

• Disease and paratistim

• Competition for resources

Density independent factors?

Factors that have the same effect whatever the population size

Trophic levels?

A positon in a food chain representing an organisms feeding relationships

What factors affect the change in population?

• Natality

• Mortality

• Immigration

• Emigration

What does sigmoids graph show?

The population grow in the exponential, transitional and plateau phases

Exponential phase?

Population is established at and ideal unlimited environment

Transitional phase?

Population growth slows as carrying capacity is reached

Plateau phase?

Something (a factor) has limited population

Cooperation?

Individuals in a population may cooperate in a variety of ways

Competition?

Members of a population have the same ecological niche and require similar resourcces

Relationships between species in close associations?

• Mutualism - Both species benefit in interactions

• Pathogenicity - One species live in another

• Paratism - One species uses another to obtain food

Relationships between species not living in close association?

• Herbivory - Primary consumer feed on producers

• Predation - One consumes another

• Interspecific competition - Two or more species require the same resources reducing the amount available

Example of mutalisim?

• Legumes and nitrogen fixing bacteria that live in root noodles

• Orchids and fungi mycorrhiza which help orchid obtain water and nutrients

• Hard corals and zooxanthellae algae living within coral tissues providing energy for photosynthesis

Endemic species?

Species native to specific locations and found nowhere else

Invasive species?

Non-native species that establish and spread in a new environment

Competitive exclusion principle?

Two species cannot occupy the same ecological niche and will eventually outcompete each other

How do invasive species succed?

• Lack of predators

• High reproductive rates

• Broad ecological niches

• Resistance to environmental stressors

What challenges do invasive species create?

• Predation and poisoning

• Resource competition

• Habitat alteration

• Disease transmission

How to study interspecific competing?

• Field manipulation

• Lav experiments

• Tests for association between species through random sampling

Predator-prey interactions?

Fundamental ecological relationships where one organisms hunts and consumes another

Why are predator prey relationships important?

• Maintains ecological balance

• prevents overpopulation

• Promotes biodiversity

• Drives natural selection

Top- down control?

Regualtion by predators or higher trophic levels

Bottom up control?

Regulation by resources availability or lower trophic levels

Chemical competition?

The use of chemicals by organisms to reduce competition for resources lie space, nutrients or light

Allelopathy?

The release of chemical by plants that negatively affect the growth of plants

Antibiotic secretion?

The release by microorganisms that inhibit the growth of other mcrobes

How does antibiotic secretion work

1. Production: Antibiotics are produced under stress or competition.

2. Release: They diffuse into the surrounding environment.

3. Effect: They kill or inhibit competing microorganisms.

Mechanisms of allelopathy?

• Leaching: Chemicals wash off leaves into the soil.

• Root exudation: Chemicals are released directly from roots.

• Decomposition: Dead plant material releases chemicals as it breaks down.

What resources limit population growth in plants and for animals?

ANIMALS

• Food

• Water

• Space

  PLANTS

• Light

• Water

• Nutrients