ESS test topic 2.1

Levels of organization

Individual— Population (same species)— Community (different populations interacting in the same area) — Community (interaction between different populations living in the same area)— Ecosystem (interaction between community and the abiotic environment)—Biosphere (all living organisms and their interactions with different spheres)

Biosphere

The global ecological system that includes all living organisms and their interactions with the atmosphere, hydrosphere, geosphere, and the lithosphere.

Atmosphere

The gaseous envelope surrounding Earth, provides CO2 for photosynthesis and O2 for respiration, and reduces harmful radiation.

Geosphere

The solid Earth, including rocks, minerals, and soils.

Hydrosphere

Water. Supports life processes, transpire of nutrients, and climate regulation

Lithosphere

Rocks, sediments. Supplies minerals and nutrients for plant growth and decomposers.

Species

A group that can interbreed under natural conditions and produce fertile offspring

Energy input

Solar radiation is captured by producers through photosynthesis and passed along food chains.

Nutrient cycling

Carbon, nitrogen, phosphorus, and water move through living organisms and the physical environment (air, soil, and water)

Environmental stability

Life depends on suitable abiotic conditions such as temperature, pH, and moisture, which affect enzyme activity, metabolism, and survival.

Major human impacts on the biosphere

1. Deforestation

2. Climate change

3. Overhunting

4. Pollution

Classification order

Domain— kingdom— phylum— class— order— family— genus— species

Classification

The systematic arrangement of organisms into groups based on shared characteristics

Size

(N) total number of individuals

Density (D)

Number of individual per unit area or volume. For late habitats, the basic idea is: D= N/A

Distribution

How individuals are spaced through the habitat (random, uniform or clumped)

Population distribution

How individuals of a species spread across their habitat.

1. Clumped

2. Uniform

3. Random

Equation for Density

D= N/A (Size/Area)

Important population factors

1. Age structure

2. Sex ration

3. Genetic Diversity

Biotic

Living influences and interactions- Predation, competition, parasitism, mutualism, food availability, and human activity. Density dependent.

Abiotic

Non-living physical and chemical influences; temperature, light, water availability, pH, salinity, dissolved oxygen, and soil texture. Density independent.

Ecological Niche

The set of unique abiotic and biotic conditions a species requites to survive, grow, and reproduce.

Habitat

The environment in which a community, species, population, or an organism lives

Common niche components

Habitat, feeding habits, temporal activity, interactions, physiological range, reproductive strategy

Fundamental niche

The full range of conditions and resources a species could use if there were no competitors, predators, or other limiting biotic interactions.

Realized niche

The part of the fundamental niche the species actually occupies after biotic interactions (especially competition) restrict it. Actual range used in nature.

Competitive Exclusion Principale

No two species can occupy exactly the same niche indefinitely in a stable ecosystem. One will exclude the other if they compete for identical resources.

Competition

−/−

An interaction where both species or individuals are harmed (−/−) as they vie for the same shared, limited resources.

Named Example: Plants compete for essential growth factors like light, water, soil, and nutrients.

Parasitism

+/−

A parasite is an organism that benefits at the expense of another

Named Example: Ectoparasites like tics and mites.

Mutualism

+/+

Symbiotic relationship where both species benefit

Named Example: Bees and flowers

Predation

+/−

One organism (predator) hunts, kills, and consumes another (pray) their populations are relative to each other

Named Example: Lion and zebra

Herbivory

+/−

Animal that feeds on plants

Named Example: Deer eating grass

Saprotropism

+/x

Organism that feeds on dead organic material, without such organisms nutrients would be recycled.

Detritivores

+/x

Gain their nutrients from dead organic matter and use enzymes to break it down

Named Example: Flies

Decomposers

+/x

Secrate enzymes to break down their food but not ‘eat it’

Named Example: Bacteria

Disease

+/x

A key biotic interaction and a density-dependent limiting factor that regulates population size.

Named Example: E.Coli, Salmonella, Athletes foot

Intraspecific competition

Carrying Capacity (K)

The maximum number of individuals of a species that an environment can sustainably support over time, given available resources. Dependent on biotic resources/interactions and abiotic conditions.

Dynamic equilibrium (in populations)

A balanced state where birth rate is about equal to death rate, so population size stays relatively stable.

Population growing beyond what the environment can support

Overshoot

Population Size (N)

The number of individuals in a population

Population Growth

The change in the population size (N) over time

Limiting Factors

Conditions (biotic or abiotic) that restrict population growth, such as, food, water, space, predation, or disease

Density- dependent factor

A factor (usually biotic) that becomes stronger as population density increases, helping regulate population size around carrying capacity (K)

• Predation, disease, breeding territory, competition for food and mates

Density- independent factor

Environmental limiting factor (usually abiotic) that affects a populations size or mortality rate regardless of population density

• Extreme weather + climate events, natural disasters, human disturbance

Biomass

The total mass of living organisms in a given area or volume

Population abundance

The total number of individuals of a specific species present within a defined area or ecosystem at a given point in time

Random sampling

A method where each individual in the population has an equal and individual chance of being selected for the sample.

• Works best for even distribution (uniform distribution)

Systematic sampling

Sampling every 'Nth' meter or grid intersection.

• Covers the whole area evenly

• Ensures a complete coverage across a large uniform study site

• Fits areas with a clear environmental gradient

• Can introduce a bias

Transect distribution

Lays a line across the study area and tales samples at regular intervals along it.

• Best for: Mapping changes in species distribution and environmental gradients

Percentage frequency

Measures how often a species appears in the same sampled quadrants

Persentage frequency equation

%= covered/total squares * 100

Species abundance

Abundance refers to the total number of individuals of a species within a quadrant

Population density equation

Population density= Total number of individuals in all quadrants/ total area of all quadrants

Lincon Index

A mathematical formula used to estimate the size of mobile organisms based on capture-mark-release-recapture method.

Lincon index equation

1. N = the estimated total population size.

2. n₁ = the number caught and ‍marked in the first sample.

3. n₂ = the total caught in the second sample.

4. n₃ = the number of marked individuals recaptured in the second sample.

Types of habitats

1. Terrestrial- Polar, coastal, arid, urban, forest

2. Aquatic- Freshwater, marine

3. Microhabitat- Small, specialised area within a larger habitat, such as ‌under a log, within leaf litter, or inside tree bark.

A habitat can support multiple niches.

Ecosystem

Ecosystem is a ‍geographic area where plants, animals and other organisms, as well as weather and landscape, work together to form ‌a bubble of life. Ecosystem is an open system.

Biotic components within an ecosystem

• Producers (plants, algae)

• Consumers (herbivores, carnivores, omnivores)

• Decomposers (bacteria, fungi)

Abiotic components within an ecosystem

Sunlight, temperature, water, atmospheric gasses, soil moisture and composition, oxygen

Closed system

A system that exchanges energy but not matter across its boundaries with the surrounding environment.

Inputs

Solar energy, water, nutrients

Outputs

Heat, water, and organic matter

Sustainability

The natural capacity of ecosystems to maintain equilibrium between resource inputs and waste outputs while continuing to support life.

Inputs and outputs balence

Inputs and outputs balance each other out so the ecosystem stays stable over time. This is called dynamic equilibrium.

Keystone species

An organism that has disproportionately large impact on its ecosystem relative to its population size.

• Disproportionate influence, habitat complexity, regulation of populations, maintenance of biodiversity, stabilization

Natural ecosystem sustainability

• Self regulating balance (inputs and outputs)

• High resilience (naturally recover overtime from natural disturbances)

• Resource continuity (energy flows and matter cycling sustain long term ecological health)

Human impact + tipping points

• Anthropogenic pressure: Overexploitation of natural resources, pollution, habitat degradation

• Critical threshold: Pushing past tipping points

• Irreversible shift: Negative changes to the ecosystem which makes the place inhabitable and loss of biodiversity