C4.1 Populations and Communities

Population

Group of same species organisms in an area.

Random Sampling

Techniques to estimate size of a population, ensuring equal chance of observation.

Quadrat Sampling

Method to estimate population of sessile organism
- A quadrant is placed over a section of habitat being studied, count organisms in frame

Transect Sampling

Sampling method along a linear path in ecosystems to study distribution

Capture-Mark-Release-Recapture

Method for estimating motile animal populations.
- Involved capturing a sample, mark each individual, & release them. After some time capture a 2nd sample and count the marked individuals.

Lincoln Index

Formula using recapture data to estimate population size.
M*N/R

Carrying Capacity

Maximum individuals an environment can support.

Density-Independent Factors of Population density

Abiotic factors affecting all populations equally.
- Includes natural disturbances such as floods, droughts, hurricanes, anthropogenic events, climate change

Density-Dependent Factors

Biotic factors affecting populations based on size.
- Such as competition for resources, predation, disease, parasitism
- Biotic factors intensify when increased

Negative Feedback control of population size

Mechanism returning population to carrying capacity.
- Counters or reverses changes in a system to maintain stability

Natality

Rate of individuals born in a population.

Mortality

Rate of individuals dying in a population.

Immigration

Movement of individuals into a population.

Emigration

Departure of individuals from a population.

Exponential Growth

Population growth in ideal, unlimited environments.
- J shaped curve
- population experiences exponential growth when resources are abundant and competition is low

Abiotic Factors

Non-living environmental factors affecting populations.

Biotic Factors

Living components affecting population dynamics.

Predation

Interaction where one organism preys on another.

Intraspecific Relationships

Interactions among individuals of the same species.
- Includes competition and cooperation

Interspecific Relationships

Relationships between individuals of different species.
- Include herbivory, predation, interspecific competition, mutualism, parasitism, pathogenicity

Fertility

Ability of individuals to reproduce successfully.

Sigmoid Growth Curve

S-shaped graph representing population growth phases.
- Initially population has exponential growth, then density dependent factors come into play, limiting rate of population growth
- Carrying capacity is reached which leads to sigmoid population growth

Interspecific Relationships

Interactions between individuals of different species.

Mutualism

Relationship where both species benefit.

Parasitism

One organism benefits at the host's expense.

Pathogenicity

Ability of pathogens to cause disease.

Herbivory

Feeding relationship between herbivores and plants.

Alien Species

Species introduced by human activity.

Invasive Species

Rapidly increasing alien species harming native species.

Endemic Species

Species found only in a specific area.

Native Species

Species naturally found in an area.

Zooxanthellae

Algae living within coral cells, aiding photosynthesis.

Root Nodules

Plant structures housing nitrogen-fixing bacteria.

Garlic Mustard

Invasive herb from Europe, disrupts native flora.

Competitive Exclusion

One species outcompetes another, leading to exclusion.

Fundamental Niche

Potential ecological role of a species without competition.

Realized Niche

Actual ecological role of a species with competition.

Chi-Square Test

Statistical test for association between species.

Degrees of Freedom

Calculated as (m-1)(n-1) in chi-square tests.

Predator-Prey Relationship

Interaction controlling population dynamics of species.

Top Down Control

Higher trophic levels influence lower levels via predation.

Bottom Up Control

Lower trophic levels affect higher levels through resources.

Allelopathy

Chemical inhibition of one plant by another.

Allelochemicals

Chemicals released by plants to suppress competitors.

Brassica Plants

Group of plants known for allelopathic properties.

Bracken Fern

Excludes other plants through allelopathic mechanisms.

Penicillin

First mass-produced antibiotic discovered by Fleming.

Contingency Table

Table used to calculate expected frequencies in chi-square.

Nutrient Competition

Plants compete for nutrients, affecting growth and survival.

Forest Invaders

Species that disrupt local ecosystems by outcompeting natives.

Field Manipulation

Experimental method involving removal of species.

Fungi Interference

Fungi essential for plant nutrient uptake can be disrupted.

Population Dynamics

Study of how populations change over time.

Germination Inhibitors

Chemicals that prevent seed sprouting in competing plants.

Trophic Levels

Hierarchical levels in an ecosystem based on energy flow.

Contaminated Dishes

Fleming's discovery of penicillin from mould contamination.

Ecological Models

Tools for understanding complex biological interactions.

Factors contributing to the overall size of a population over time

natality, mortality, immigration, emigration