GCSE AQA BIOLOGY: 7.1, 7.2, 7.4 - Ecology

What is ecology?

The study of how organisms interact with each other and their abiotic environment.

What is an individual a part of?

A population of organisms of the same species

What is a population a member of?

A community of varying populations, that is part of a larger ecosystem

What do species depend on other species, within a community?

Food, shelter, pollination and seed dispersal

What is an individual?

a single organism

What is population?

total number of organisms of the same species that live in a specific geographical area

What is a community?

A group of interdependent populations living and interacting in an area.

What is an ecosystem?

A biological community of interacting organisms and their physical environment.

What are the factors of an environment?

Soil, climate, rainfall

What is interdependance?

When organisms depend on each other to survive within a community

What changes in an environment can damage interdependence?

If one species is removed or becomes very abundant

What does this change in population lead to?

The balance is destroyed and it can have a knock on effect that affects every species in a community

How are animals dependant on plants?

As food sources and for oxygen

How are Decomposers reliant on organisms?

Their dead organic matter is needed as food

How do insects rely on plants?

As a food source (nectar)

How do plants rely on insects?

For pollination

How do plants rely on Decomposers?

They need the nutrients that Decomposers break down into simpler molecules

What may unexpectedly happen is a consumer looses a food source?

Their population may experience no net change as they turn to another food sources

What is a stable community?

One where all species and environmental factors remain relatively constant or change in a regular predictable cycle so that population sizes remain fairly constant.

How can environmental factors change in a regular predictable cycle?

Seasons

What are we now more than ever discovering?

The importance of the balance of nature and its fragility

Give 3 examples of stable communities?

Tropical rainforests, mature coral reefs and ancient oak woodlands

Why are stable communities difficult to replace?

They take a long time to evolve

How do population numbers change over time?

They stabilise from high fluctuation over time

Why will the numbers of individuals in different populations of a stable community NOT be the same?

As consumers usually eat more than 1 of their prey

What are abiotic factors?

nonliving factors

What are biotic factors?

living things

What do plants compete for?

Light, space, water and mineral ions from soil

What do animals compete for?

Food, mates and territory

What are organisms in a stable community?

Well adapted to their environment

What are abiotic factors for the soil?

Soil pH, mineral content, moisture levels

What are abiotic factors for wind?

Wind intensity and direction

What are abiotic factors for the atmosphere?

CO2 levels for plants, temperature and light intensity

What is an important abiotic factor for aquatic organisms?

O2 content of water

What is intraspecific competition?

competition between individuals of the same species

What is interspecific competition?

competition between individuals of different species

How are plants adapted for reproduction?

- brightly coloured flowers

- sweet scents

- nectar production

- adapted seeds

How are seeds adapted for wind dispersal?

Lightweight

How are seeds adapted for water dispersal?

Hollow/ low density = buoyancy

How are seeds adapted for animal dispersal?

Fruit production/ hooks to latch on

What happens when seeds fall close together?

There is a competition between seedlings for resources

What are 2 qualities of successful seedlings?

1. Germinate quickly

2. Open their leaves the fastest

Why does germinating quickly help a seed?

Their roots grow down into the soil first = absorb more water and mineral ions = OUTCOMPETE OTHERS

Why does opening their leaves the fastest help a seed?

Photosynthesise earlier = more glucose/energy = more growth = reach sunlight first

What are the biotic factors that can affect ecosystems?

- food availability

- new predators

-new pathogens

- new competition

Why does outcompeting lead to the extinction of the lesser species?

Lower survival rate due to lack of resources = numbers of the species fall below what is needed to breed/ replacement rate

What do organisms need to compete, survive and reproduce?

A supply of materials form their environment and other living organisms

What are adaptations?

Features that enable organisms (including microorganisms) to survive in the conditions in which they normally live

What are the 3 types of adaptation?

structural, behavioural, functional

What are structural adaptations?

Physical parts/ features of an organism

What are behavioural adaptations?

The ways an organisms behaves/ acts

What are functional adaptations?

Altered biological processes within the organism

Give 2 examples of structural adaptations?

Furrow bees having yellow and black stipes like wasps - similar to the hornet moth

How does white fur help an animal?

Poor emitter of heat = less heat loss

How do small projections help an animal?

Smaller SA:V ratio = less heat lost per unit of mass

Give 2 behavioural adaptations?

- beetles playing dead

- male cockatoos beating on hollow branches with sticks to attract a mate

Give 2 functional adaptations?

-hibernation

- sea spiders have automatic muscle contractions that move O2 around their bodies

What happens during hibernation?

the animals metabolic rate drops with a resulting decrease in body temperature, heart rate and breathing rate = barely any glucose needed

What are extremophiles?

organisms that live in extreme environments

What are the features of an extreme environment?

- Very high/low temperatures

- high salt levels

- very high/ low pH

- very high pressures

Give 2 examples of a very high salt levels in an environment?

- hyper-saline/ soda lakes

What type of organism are most extremophiles?

Bacterial

Give an example of a bacterium living in an extreme environment?

A bacterium living in a deep sea vent

How are different species connected?

By feeding relationships

How can feeding relationships within a community be represented?

With food chains or food webs

What do the arrows in a food chain/ web represent?

The direction of energy flow

What organisms are the producers of biomass for all life on earth?

Photosynthetic organisms

Which trophic level is home to photosynthetic organisms?

The 1st trophic level

What is a trophic level?

the position of an organism in a food chain or food web

Which organisms do not fit neatly into 1 trophic level?

Decomposers

What type of organisms are Decomposers?

fungi and bacteria

How do Decomposers feed?

Extracellular digestion

What is the 1st step of extracellular digestion?

- secreting enzymes into dead organism matter to digest it

What is the 2nd step of extracellular digestion?

They then absorb the soluble food molecules via diffusion

What is the 3rd step of extracellular digestion?

Excess mineral ions are returned to the environment

What is humus?

The layer of decaying organic material that makes soil dark and fertile

What are the 3 forms of feeding?

Photosynthesis, consumption and extracellular digestion

Why are food chains flawed?

As animals usually have more than 1 food source

What is a trophic cascade?

an ecological process that starts with a change at the top of the food chain and impacts the populations of those organisms all the way down the chain

How is a food web made?

By combining many food chains

What is still a flaw with food webs?

Decomposers are still not represented

What is the ultimate source of all food chain's energy?

The sun

How to plants and algae use the sun's energy?

Plants/algae transduce the light energy of the sun into chemical energy - stored in the cells fo the plant

How does photosynthesis add to the biomass?

The new plant material made from photosynthesis adds to the biomass

How do we often measure biomass?

As the dry mass of a biological materials in grams - by removing all of the water

What is the problem with dry biomass measuring?

It kills the organism

What is the problem with wet biomass measurements?

They are inaccurate due to water content and it increase the magnitude of error

How is biomass passed along a food chain?

Via consumption

How do we represent the flow of biomass?

With a pyramid

What does each block of the biomass pyramid represent?

The total mass of all of the individuals in the population of that species in the ecosystem

What is the width of a biomass block proportional to?

It is proportional to the amount of biomass

Why are producers inefficient at transducing the sun's energy?

They only transfer around 1% of the sun's energy

Why are food chains also inefficient?

Only around 5% is transferred from plant to animal and only 10% is transferred from animal to animal

How is biomass lost in a food chain?

- not all parts of a plant/animal are edible

- not all parts of a plant are digestible, so are therefore lost as faeces

- a lot of the energy is lost from cellular respiration in the form of heat

What parts of a plant/ animal might not be edible?

Thorns/ bones/ roots

What parts of a plant might not be digestable?

Cellulose

What does sessile mean?

immobile

What are the difficulties for primary consumers?

- difficult to digest cellulose

- have to find enough pliant material for sufficient caloric intake

What are the advantages of being a primary consumer?

Food source doesn't move so no energy wasted on hunting

What is a difficulty for a secondary/ tertiary consumer?

They have to hunt and catch prey before eating, so more energy is lost via respiration