ESS revision

Ecology

The study of interrelationships between living organisms and their biotic (living) and abiotic (non-living) environment

Biosphere

The parts of earth where life exists

Atmosphere

The gases surrounding the planet

Hydrosphere

The water containing parts of Earth

Lithosphere

The underground parts of Earth

Species

A group of organisms that can interbreed and produce fertile offspring, and share the same characteristics

CITES

Convention on International Trade of Endangered Species

Liger

Offspring of a tiger and lion that is infertile, hence called a hybrid and not a specie.

Population

A group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding

Classification

The identification system of organisms which allows for a prediction of characteristics.

Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Hierarchal classification system

The higher ranks contain more organisms with less similarity between them and the lower ranks contain fewer organisms with more similarities.

Clades

The lines that are in the family of tree diagrams. Shows a group of species (from a taxonomic group) that evolved from a common ancestor.

Node

Where characteristics branch and species diverge

Root

Point prior to any divergence where the organisms share certain characteristics

Binomial nomenclature

Binomial naming system

Dichotomous keys

Quantitative and qualitative factors are considered (like number of legs, weight, height, etc.). Can be done in a graphical or written form - series of paired statements organised sequentially. Used to identify and organism.

Comparison of species with reference to collections by taxonomists

Comparing unknown specimens to those with similar characteristics that have been already identified and classified. Relies on the taxonomist’s expertise and quality of the reference collection.

Deoxyribonucleic acid (DNA) surveys

Analysing an organism’s DNA to determine its species. Compares the DNA sequence of the specimen with known sequences from a very large number of species, stored in large computer databases. Provides a precise and reliable identification, especially for closely related species.

Abiotic factors

Non-living physical factors that may influence an organism in an environment. Eg. Water level, humidity, temperature, salinity, soil mineral content, % of gases in the air, light, pollution, pH of soil.

Biotic factors

The living components of the environment that affect individuals. Eg. Parent material, parasites, predators, fungi, competitors, human activity, bacteria, plants, animals.

Ecological niche

the role or position a species occupies within an ecosystem, including all the biological, physical, and chemical factors it requires to survive, reproduce, and maintain a stable population.

Niche overlap

When two organisms occupy the same niche in the same habitat, they begin to compete

Carnivory

Predator-prey relationships

Mutualism (symbiosis)

Two species interacting with each other where both species benefit.

Commensalism

Two species interacting with each other and one species is benefiting while the other is unaffected.

Parasitism

Two species interacting while one species benefits and the host species (that the parasite lives on or off) is harmed.

Competition

The struggle between individuals or different populations for a limited source

Intra specific competition

Competition of individuals of the same species for limited sources.

• resource strain = does not support unlimited population growth.

• Reduced growth rate = slower population stabilisation

• Niche partitioning = individuals specialise / adjust their ecological niches to minimise direct competition.

• Niche selection = favouring traits that improve access to resources or enhance survival under competition.

Interspecific competition

When individuals of different species compete for the same limited resources (eg. Food, space, mates).

• two different species require the same resources

• Species directly interact

• Species evolve or adjust to different resources or occupy different habitats to resolve competition: realised niche

• Local extinction of weaker species

• Species can coexists if they can occupy different ecological niches or if they evolve strategies that minimise direct competition.

Fundamental niche

The broadest range of habitats a species can occupy and the roles it can fulfil given the adaptations.

Realised niche

The actual mode of existence given competition with other species and its zone of tolerance

Competitive exclusion principle

If two species occupy the same niche, one will decline or both will narrow their niches to avoid overlap.

Tolerance of a species depends on?

The abiotic factors - that’s how the fundamental niche of an organism is formed.

Population growth and decline depends on

Birth rate, limiting factors: starvation/availability of food, disease, predation, hunting, natural disasters.

R-strategists

• Species that focus on rapid reproduction and high growth rates.

• They typically produce many offspring but invest little energy or resources in each individual.

• Offspring are often small, grow quickly, and have a low survival rate.

• r-strategists are adapted to unstable or unpredictable environments where survival depends on quickly taking advantage of available resources.

• Examples: Bacteria, insects (e.g., flies), and some plants (e.g., dandelions).

Characteristics of r-strategists:

1. Short lifespan.

2. Early reproduction.

3. Small body size.

4. High population growth rate.

K strategies

Definition: Species that produce fewer offspring but invest heavily in their survival and development.

• They are adapted to stable environments, where competition for resources is significant, and long-term survival is key.

Characteristics:

1. Long lifespan.

2. Delayed reproduction.

3. Larger body size.

4. Low population growth rate.

5. High survival rate per offspring.

Examples: Elephants, whales, and humans.

Carrying capacity

The maximum number of individuals that an ecosystem can support sustainably

Density dependent factors

Affect the population only when it reaches a certain density, due to the many interactions that happen as the population size gets bigger.

Eg. Competition, disease, parasitism, predation = biotic factors

Waste building up

Often cause intraspecific competition

Density Independent factors

Control populations no matter what the density of the population is. Tend to be abiotic.

Eg, sunlight, temp, water & natural disasters, human activities.

J curve

Population growing at its biotic potential

• exponential growth

• Very steep

• No limiting factors

S curve

Limiting factors slow the growth and the graph curves as it approaches the carrying capacity.

Non-motile organisms

Plants, lichens, mollusks, are often measured with quadrants and transects to measure percentage cover or percentage frequency.

Motile organisms

Organisms that can move. Eg. Fish, rabbits, insects, are often sampled through direct count and sampling

Random sampling

Involves selecting locations within the study area at random to count individuals.

Strength: reduces bias, as every part of the study area has an equal chance of being selected.

Limitations: might miss areas with particularly high or low population densities leading to inaccurate estimates.

Systematic sampling

Involves taking samples at regular intervals within the study area.

Strengths: When you need a straightforward method that ensures thorough and even coverage of the study area, and when the population is relatively uniform or randomly distributed without regular patterns.

Limitations: might introduce bias if the population has a pattern that coincides with the sampling interval, such as regular clustering.

Random sampling method

Randomly sample 5 quadrants - take the mean of the 5 quadrants. Multiply the mean by the area of the grid: 10 × 10 = 100

Transect sampling

Involves sampling along a line / path that runs through the study area.

Use when you need to study changes across an environmental gradient and to see how population abundance varies along a specific path or direction.

Line transect

Organisms found at the regular sample points are recorded.

Belt transect

Quadrants are placed at regular sample points and the abundance of the organisms within each other is recorded

Capture-mark-release = Lincoln index

1. Capture as many individuals as possible and mark them (without making them more visible to predators).

2. Release the captured individuals and allow time for reintegration with the population.

3. After some time, recapture as many individuals as possible.

4. Count how many individuals are marked and unmarked

5. Lincoln index → proportion of marked and unmarked individuals in the recapture = proportion within the whole population.

6. Pop. Size estimate = (n.o. Individuals caught and marked initially x total number of individuals recaptured) / number of marked individuals recaptured.

7. It assumes that there’s no migration into/out of the population and that there was complete mixing of marked and unmarked individuals.

Habitat

Natural environment in which a particular species lives, grows and thrives. Includes all physical, chemical and biological factors that support the existence of that species.

Ecosystem

A community of living organisms interacting with each other and their physical environment (like air, water and soil) forming a system where energy and nutrients cycle through.

Species

A group of organisms that can interbreed and produce fertile offspring, sharing common characteristics and genetic traits.

Population

A group of individuals of the same species living in a specific area, at the same time, capable of interbreeding and interacting with each other.

Community

A group of different species living and interacting in the same area, sharing resources and influencing each other’s survival and behaviour.

Keystone species

A specie that plays a critical role in maintaining the structure of the ecosystem in which they live.

Yellowstone wolves

1. Grey wolves were the apex predators in the Yellowstone park

2. Played a critical role in controlling populations of large herbivores: elk, deer, and moose, maintaining balance in the ecosystem by preventing overgrazing and helping to shape the structure of the entire landscape (river banks).

   By keeping Elk numbers in check, wolves allowed vegetation such as willow and aspen to regenerate, which in turn benefited other species like bears and birds.

3. 1900s - threat to live stock → aggressive government sponsored extermination campaigns.

4. 1920s - extirpation (local extinction) of wolves from Yellowstone.

5. 1973 - Endangered Species Act (ESA) provided legal protection for grey wolves, and by mid 1970s, wildlife biologists and conservationists bagan discussing the idea of reintroducing wolves to Yellowstone

6. 6. 1980s-1990s: noticing the important role of wolves and planning the idea to reintroduce wolves into the Yellowstone park

7. 1995: reintroduction of wolves to Yellowstone began as part of a broader effect to restore balance to the park’s ecosystem.

Controversy: balance between wildlife conservation and livestock protection continues to be a source of tension in the region.

Tipping point

The minimum amount of change within an ecosystem required that will destabilise it, causing it to reach a new equilibrium or steady state. (Irreversible change).

Planetary boundaries model

Defines a safe operating space for humanity in terms of 9 key environmental processes that are crucial for maintaining the stability of the Earth system. Exceeding the boundaries could lead to irreversible and catastrophic environmental changes:

• novel entities

• Climate change

• Biosphere integrity

• Land system change

• Biochemical flows

• Ocean acidification

• Fresh water use

• Atmospheric aerosol loading

• Stratospheric ozone depletion

IUCN Red List

Monitoring population numbers.

Good luck

Part 1