Biology Unit 3: Ecology

Biodiversity

The variety of species and ecosystems.

Genetic Diversity

The number of different alleles possessed by a species.

Species Diversity

The number of different species in a particular ecosystem at a given time.

Ecosystem Diversity

The number of different ecosystems or biomes and the variation between them.

Ecology

The study of plants and animals in relation to their total environment.

Abiotic Factors

Non-living factors such as soil pH, temperature, and salinity that affect growth and survival.

Biotic Factors

Living factors like species interactions, competition, and predator-prey relationships.

Quadrats

A frame used for sampling organisms within a designated area.

Transects

Lines marked out for sampling organisms at regular intervals.

Species Richness

The number of different species within a given area.

Simpson’s Diversity Index (SDI)

Measures the probability that two randomly selected organisms are from different species.

Percentage Frequency

The percentage of quadrats in which a species is present.

Percentage Cover

The percentage of an area covered by a particular organism.

Temporal Scale

Changes in an ecosystem over time based on the lifespan of species.

Spatial Scale

The distance between habitat patches.

Mutualism

A type of symbiosis where both species benefit from the interaction.

Amensalism

A type of symbiosis where one species is negatively affected while the other is unaffected.

Commensalism

A type of symbiosis where one species benefits and the other is neither helped nor harmed.

K-strategists

Species characterized by longer lifespans, low reproduction rates, and parental care.

r-strategists

Species characterized by shorter lifespans, high reproduction rates, and little to no parental care.

Clade

A group of organisms that consist of a common ancestor and all its lineal descendants.

Ecological Niche

the role and space that an organism fills in an ecosystem, including all it’s interactions with the biotic and abiotic factors of it’s environment 

Fundamental Niche

All possible resources a species can use without competition.

Realised Niche

The actual resources and habitats a species uses in the presence of competition.

Competitive Exclusion Principle

Two species competing for the same limited resources cannot coexist stably.

Keystone Species

a plant or animal that plays a unique a crucial role in the way an ecosystem functions. controls populations, have a large variety of prey. They have a much larger effect on the ecosystem than their abundance might indicate. 

Parasitism

A type of symbiosis where one species benefits at the expense of the other, often by living on or in the host.

Predation

An interaction where one organism (predator) kills and consumes another organism (prey).

Interspecific Competition

Competition occurring between different species for the same limited resources.

Population

A group of individuals of the same species living in the same geographic area at the same time.

Community

All the populations of different species that live and interact in the same area.

Ecosystem

A biological community of interacting organisms and their physical environment.

Trophic Level

The position an organism occupies in a food chain or food web, describing its role in energy transfer.

Carrying Capacity

the size of the population that can be supported indefinitely on the available resources and services of that ecosystem  

Why is Biodiversity important?

It ensures ecosystem stability, provides resources (food, medicine), supports ecosystem services (pollination, water purification), and contributes to cultural and aesthetic values.

Examples of Abiotic Factors:

Light intensity, water availability, pH levels, mineral nutrient concentrations, temperature, salinity, and humidity.

Examples of Biotic Factors:

Competition for resources, predation, herbivory, disease, parasitism, and symbiotic relationships (mutualism, commensalism).

Interpreting Simpson’s Diversity Index (SDI) values:

A value closer to 1 indicates higher diversity, meaning a greater probability that two randomly selected individuals will be from different species. A value closer to 0 indicates lower diversity.

Characteristics of K-strategists:

Long gestation period, high parental investment, few offspring, slower development, late sexual maturity, and usually thrive in stable environments. Examples include elephants, whales, and humans.

Characteristics of r-strategists:

Short gestation period, minimal to no parental investment, many offspring, rapid development, early sexual maturity, and typically thrive in unstable or changing environments. Examples include insects, bacteria, and weeds.

What are the main Trophic Levels?

Producers (autotrophs), Primary Consumers (herbivores), Secondary Consumers (carnivores/omnivores that eat herbivores), Tertiary Consumers (carnivores/omnivores that eat secondary consumers), and Decomposers.

When would Quadrats be used for sampling?

For estimating population density, frequency, or cover of sessile or slow-moving organisms in a defined area, especially in habitats with relatively uniform distribution.

When would a Line Transect be used?

To study how species distribution or abundance changes along an environmental gradient (e.g., from water to land, or up a hill), by recording organisms that touch a designated line.

When would a Belt Transect be used?

To obtain more detailed quantitative data about species distribution and abundance along a gradient, by placing quadrats at regular intervals along a line.

When would Randomised Sampling be used?

To avoid bias and ensure that all areas have an equal chance of being sampled, suitable for habitats that appear uniform and lack obvious gradients, allowing for statistically robust conclusions about the population.

What is Ecological Succession?

The process by which the structure of a biological community evolves over time, often following a disturbance, leading to changes in species composition

What is a Biome?

A large naturally occurring community of flora and fauna occupying a major habitat, defined by global climate patterns and dominant vegetation types (e.g., forest, desert, tundra)

What is the 10%10% Rule in ecology?

A principle stating that on average, only about 10%10% of the energy from one trophic level is transferred to the next trophic level; the remaining 90%90% is lost as heat during metabolic processes or is not consumed.

What is a Limiting Factor?

Any environmental factor (such as food, water, light, space, or predation) that restricts the number of individuals that can be supported by an ecosystem, thereby limiting population growth or distribution.

Stratified Sampling

a type of sampling in which a sample is taken of each strata (group) of the population

what is parapatric speciation

what is allopatric speciation

what is sympatric speciation