Bio ecosystems revision

Summative t2- all terms

ecosystem

The complex and diverse system made up of living organisms and their connection to each other and the environment.

Biotic Factor

Living things within an ecosystem (such as plants, animals and bacteria)

Abiotic factor

Non-living components of an ecosystem, including factors like temperature, sunlight, water, and soil.

Community

A group of different species that live together in a specific area, interacting with each other and their environment.

Habitat

The natural environment where a species or community of organisms lives, providing the necessary conditions for survival and reproduction.

Purpose of habitat

To provide essential resources and conditions for survival, reproduction, and growth of organisms, such as food, water, shelter, and mating opportunities.

Population

A group of individuals of the same species that live in a specific area and interact with each other, sharing resources and space.

Species

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

Mutualism

A type of symbiotic relationship where both species benefit from the interaction.

Commensalism

A type of symbiotic relationship where one species benefits while the other is neither helped nor harmed.

Parasitism

A type of symbiotic relationship where one species benefits at the expense of the other, often harming the host.

Predation

A type of interaction where one organism, the predator, kills and consumes another organism, the prey.

Herbivory

A type of interaction where an herbivore feeds on plants or plant parts, benefiting the herbivore while potentially harming the plant.

Competition

A type of interaction where two or more organisms vie for the same resources in an ecosystem.

What do organisms compete for in ‘competition’

resources such as food, water, space, and mates.

ammensalism

A type of interaction where one organism is harmed while the other is unaffected, often involving the release of harmful substances.

Where does energy for most ecosystems come from?

The sun, through photosynthesis in plants.

What trophic level begins the energy cycle?

The primary producers or autotrophs.

Where is energy stored?

In biomass of organisms/biological molecules.

How is energy used by an organism?

Energy is used by organisms for growth, reproduction, movement, and maintaining homeostasis.

What trophic level consumes primary producers?

The primary consumers, or herbivores.

What is the 10% rule?

The 10% rule states that only about 10% of the energy from one trophic level is transferred to the next level in an ecosystem, while the rest is lost as heat or used for metabolic processes.

How do decomposers consume energy?

Decomposers consume energy by breaking down dead organic matter or consuming poop, recycling nutrients and matter back into the ecosystem for use by producers.

What is the movement of energy and matter?

Energy flows, matter recycles

Trophic levels

are the hierarchical levels in an ecosystem that represent the flow of energy and nutrients through food chains

The five trophic levels

Primary producers (autotrophs), primary consumers, secondary consumers, tertiary consumers, quaternary consumers

Decomposer

On organism that decomposes organic material

Detritus

Dead organic matter (dead plants, animals, animal waste or shed parts, like skin and leaves) that is an energy source for decomposers and detritivores.

Pyramids of number

ecological diagram that shows number of individual organisms at each trophic level in food chains or food webs

What happens to numbers in pyramids of number

Usually, numbers decrease as you go up the pyramid because energy and biomass are lost between levels

Pyramids of biomass

ecological diagram that represents total mass of living organisms at each trophic level in food webs, food chains or ecosystems. it shows how much living or organic matter is available at each level.

pyramids of energy

an ecological diagram that shows the flow of energy through each trophic level in an ecosystem over a given time. Energy decreases as it moves up the food chain due to the ten percent rule

Carbon cycle

Cycle where carbon atoms move between atmosphere, biosphere, oceans and geosphere. Shows how carbon is exchanged among living organisms, the environment and fossil fuels

key processes of the carbon cycle

Photosynthesis, respiration, decomposition, combustion, ocean and fossilisation

Photosynthesis in the carbon cycle

Plants absorb carbon dioxide (CO₂) from the atmosphere and convert it to glucose using sunlight (CO₂ + H₂O → C₆H₁₂O₆ + O₂)

Respiration in the carbon cycle

Plants and animals break down glucose to release energy, returning CO₂ to the atmosphere (C₆H₁₂O₆ + O₂ → CO₂ + H₂O + energy)

Decomposition in the carbon cycle

When organisms die, decomposers break them down, releasing carbon into the soil and atmosphere.

Combustion (burning) in the carbon cycle

Burning fossil fuels or biomass releases stored carbon (as CO₂) into the atmosphere.

Ocean in the carbon cycle

Oceans absorb CO₂ from the air; some becomes part of marine organisms or forms carbonate sediments.

Fossilisation in the carbon cycle

Over millions of years, some dead organisms are compressed into fossil fuels, trapping carbon underground.

Key pathways in the carbon cycle

• Atmosphere ↔ Plants (via photosynthesis & respiration)

• Animals ← Plants (via feeding) → Atmosphere (via respiration)

• Dead organisms → Decomposers → Atmosphere or soil

• Fossil fuels → Combustion → Atmosphere

• Atmosphere ↔ Oceans

What is the importance of the carbon cycle?

Regulates Earth’s climate and temperature

Nitrogen cycle

cycle that shows how nitrogen moves between the atmosphere, soil, water, plants, animals, and microorganisms.

Nitrogen cycle importance

Nitrogen is needed to build proteins, DNA and other vital molecules in living organisms. Most organisms cannot use nitrogen in gas form so the nitrogen needs to be converted.

Key processes

Nitrogen fixation, nitrification, assimilation, ammonification (decay), denitrification

Nitrogen fixation

Atmospheric N₂ gas is converted into ammonia (NH₃) or ammonium (NH₄⁺) by:

• Nitrogen-fixing bacteria (in soil or plant roots like legumes)

• Lightning

• Industrial processes (e.g., Haber process)

Nitrification

Ammonia or ammonium is converted into nitrites (NO₂⁻) and then into nitrates (NO₃⁻) by nitrifying bacteria in the soil.

Assimilation

Assimilation

• Plants absorb nitrates from the soil and use them to make proteins and other compounds.

• Animals obtain nitrogen by eating plants or other animals.

Ammonification (decay)

Decomposers break down dead organisms and waste, releasing ammonia or ammonium back into the soil.

Denitrification

Decomposers break down dead organisms and waste, releasing ammonia or ammonium back into the soil.

Nitrogen cycle summary

• Atmosphere (N₂) → Fixation → Soil Ammonia/Nitrates → Plants & Animals

• Death & Waste → Decomposition (Ammonification) → Soil Nitrogen

• Soil Nitrates → Denitrification → Atmosphere

primary succession

gradual development of ecosystems in an area where no life previously existed, starting from bare rock or a newly formed surface with no soil or organic matter.

When does primary succession occur?

• After volcanic eruptions (lava flows)

• Glacier retreats

Stage of primary succession

1. Bare Surface

   • No soil, no life – just rock or sand.

2. Pioneer Species

   • First organisms to colonize (e.g., lichens, mosses) that can survive in harsh, nutrient-poor conditions.

   • They help break down rock into soil.

3. Soil Formation

   • As pioneer species die and decompose, they add organic matter, forming thin soil.

4. Intermediate Species

   • Grasses, ferns, and small shrubs begin to grow in the new soil.

5. Climax Community

   • A stable, mature ecosystem (e.g., forest, grassland) is established, with complex food webs.

Secondary succession

natural process of ecosystem recovery that occurs in an area where a community has been disturbed or destroyed, but soil and some organisms still remain.

When does secondary succession occur?

• After bushfires

• Following floods or hurricanes

stages of secondary succession

• Disturbance Occurs

  • A natural disaster or human activity removes vegetation, but soil remains intact.

• Pioneer Species Reappear

  • Fast-growing plants like grasses and weeds colonize first.

• Intermediate Species Grow

  • Shrubs, small trees, and more animal life return as the ecosystem stabilizes.

• Climax Community

  • A stable, mature ecosystem is re-established (e.g., forest, grassland), possibly different from the original.

Key differences between primary and secondary succession

Primary succession starts with bare rock and secondary succession starts with soil and even life. Primary succession is very slow (hundreds to thousands of years) and secondary succession is faster. The pioneer species of primary succession are lichens and moss, while secondary succession is grass and weeds. Different occuring events (volcanic eruption + glacier retreat vs. fire + flood)

Major human impacts on ecosystems and biodiversity

Deforestation (loss of habitat)
Air pollution (acid rain + climate change)
Water pollution (harms aquatic life)
Soil contamination (affects plant growth + food chains)
Climate change (alters weather patterns, sea levels + temperature)
Invasive species (predators/competition for natives)
Overhunting/overfishing
fragmentation (cities +roads destroying ecosystems)

biodiversity

the variety of all life forms (genes, species, ecosystems).

Impact of loss of biodiversity

• weakens ecosystem resilience (ability to recover from disturbances).

• Reduced genetic diversity makes species more vulnerable to disease and environmental change.

Solutions/mitigation to human impact

• Conservation programs and protected areas (e.g., national parks).

• Sustainable resource use (e.g., responsible fishing, logging).

• Climate action (e.g., reducing emissions, using renewable energy).

• Restoration ecology – replanting native species, rewilding areas.

• Education and legislation – policies to protect endangered species and ecosystems.

Adaptation

Adaptation is the process by which organisms become better suited to their environment over time. It happens through natural selection, where individuals with traits that improve survival and reproduction are more likely to pass those traits to the next generation.

Natural selection process

• Variation

  • Individuals in a species have genetic differences (e.g., fur thickness, leaf size).

• Environmental Pressure

  • Conditions such as climate, predators, or lack of water create challenges for survival.

• Selection

  • Individuals with advantageous traits survive better and reproduce more.

• Inheritance

  • Beneficial traits are passed on to offspring through genes.

• Adaptation Over Time

  • Over many generations, these traits become more common, and the population becomes better adapted.

classification of organisms (taxonomy)

Classification is the scientific method of grouping organisms based on shared characteristics and evolutionary relationships.

Importance of taxonomy

It helps scientists:

• Identify and study organisms

• Understand evolutionary relationships

• Communicate clearly using universal names

taxonomy hierarchy

• Domain

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

Binomial system of nomen clature

The binomial system is a method of naming species using two Latin words:

• The Genus name (capitalised)

• The species name (lowercase)

Rules for binomial system

written in italics/underlined when handwritten

Role of animals in the carbon cycle

Animals release carbon dioxide during respiration. When animals die, decomposition also produces carbon dioxide.

Role of plants in the carbon cycle

Plants do photosynthesis and use carbon dioxide from the atmosphere and water from the soil to prepare glucose and produce oxygen gas. This process helps to maintain the balance of carbon dioxide in the atmosphere

Plants also respire and release carbon dioxide back into the atmosphere. Plants die and release carbon dioxide through decomposition of plant material,