1.7 Ecological relationships and energy flow

Ecology

distribution of living organisms and relationships between them

Ecosystem

area where community of organisms live and are affected by range of environmental factors

Biodiversity

measure of the number of species living in an area

Habitat

specific area or environment where a population lives and breeds

Population

number of organisms of single species living in an area

Community

several populations of different species living in habitats close together

Abiotic factors

non-living factors e.g temperature and light

Biotic actors

living factors e.g effect of predators or competitors

Organism

An individual living thing that is part of a much larger ecosystem

Predator-prey relationship

The interdependent interaction between an organism that eats another organism and the consequent effect one species has on the other

Removing a species from an ecosystem

If one species or population is removed from an ecosystem it can have a significant impact on the entire community

Stable community

One where all the species and environmental factors are in balance so the population sizes remains fairly constant

Resources

To survive and reproduce, organisms require a supply of materials from their surroundings and from the other living things there

Competition

Organisms need resources that are often scarce to survive and reproduce, so most organisms must compete with one another to obtain or claim these resources

Competition between species

Also known as interspecific competition, different species may compete for resources such as food or territory

Competition within a species

Also known as intraspecific competition, individuals within a species may compete for resources such as food, territory or mates

Reasons for competition in animals

Food, access to water, mates, shelter or territory

Reasons for competition in plants

Light for photosynthesis, space, water and mineral ions in the soil

Adaptation

Organisms have specific features that enable them to survive in the conditions in which they normally live

Examples of adaptations

Large surface area to volume ratio to keep cool in hot environments, thick fur in cold environments, camouflage to hide from other organisms, feet with large surface area to trek on sand or snow

Light intensity

An abiotic factor that plants compete for, plants require energy from sunlight to photosynthesise

Water levels

An abiotic factor that some organisms may compete for, moisture in soil is necessary for the survival of most plants and specific humidity levels or water sources are essential for most organisms

Soil mineral content

An abiotic factor that plants compete for, plants require minerals for sufficient plant development

Food availability

A biotic factor that animals compete for, animals depend on other animals or plants as sources of food and energy

Predators

A biotic factor that may affect the size of a population, organisms capable of predation can affect the levels of animals or plants in an ecosystem

Pathogens

A biotic factor that may affect the size of a population, organisms can be severely affected by the introduction of diseases that are caused by pathogens

One species outcompeting another species

A biotic factor that may affect the size of a population, if one species is outcompeted the population of that species may decline as individual organisms may not be able to obtain the resources needed to survive and reproduce

Pollution

An abiotic factor that may affect the size of a population, toxic chemicals, substances and gases can affect the distribution and abundance of species in an area

Structural or morphological adaptation

Physical features that allow organisms to compete, such as sharp claws in animals to catch prey or broad leaves to optimise photosynthesis in plants

Behavioural adaptation

Behaviours that give organisms an advantage, such as nocturnal activity in desert animals to stay cool or plant shoots growing towards light in plants

Distribution of a species

The range or spread of the individuals of a species in an area

Factors affecting the distribution of a species

Typically abiotic factors such as light intensity or soil mineral content but can also include biotic factors such as competition

Abundance of a species

The amount of individuals of one species found in an area at the same time

sampling techniques

Sampling

process used to give good estimate of number of an organism in a particular area

Quadrat

A square frame that is thrown or placed to count individuals of a specific species, typically used to estimate a population size in an area

Uses of quadrats

Can assess the number of individuals of one species, can be used to determine species richness or the variety of species in an area, can be used to work out percentage cover which is an estimation of the area that one species covers in a quadrat

Transect

A line or tape measure that covers the length of a specific area and can be used as a reference to measure the distribution of a species at regular intervals

Belt transect

A combination of quadrats and line transects, a quadrat is placed at specific intervals of the transect and can be used to measure the distribution and abundance of a species

Population size or density

The estimated size of the population of one species found in the same area at the same time

Random sampling

Sampling techniques should be random to avoid bias and ensure an investigation is fair

Total population size equation

(Total field area/area sampled) x total number of individuals of a specific species counted

Area sampled calculation

Area of one quadrat multiplied by the number of quadrats used in an investigation

Species richness

The number of different species in a community, can be assessed using belt transects

Kite diagram

A diagram used to visualise the abundance and distribution of different species, using belt transect data

Zonation

The distribution of plants or animals into specific zones that results from different abiotic and biotic factors

Pooters

Containers used to collect insects easily for sampling, without harming them

Nets

Can be used to collect organisms by sweep netting through long grass or leaves of trees or in aquatic environments by kick sampling where a net is held downstream

Pitfall traps

A hole dug in the ground to catch small invertebrate species for sampling, the traps should be checked frequently to prevent organisms being harmed or eaten by other organisms

Capture-recapture technique

Organisms are trapped and marked and later recaptured after appropriate mixing time, used to estimate how many organisms are in a population

Tape measures

Can be used to work out the area of a field or can act as a line transect to measure species distribution

Mean average

The total sum of the data values divided by the number of times the data was recorded

Common species

An easily observable and frequent species such as a daisy or dandelion

Random number generator

A computer can randomly assign coordinates for quadrat placement or numbers can be drawn at random from a bag to avoid bias

Valid results

To ensure results are valid the number of quadrats placed or thrown can be increased or the investigation could be repeated

Expected results for transect investigation

A factor such as light intensity can affect the distribution of a plant species, a shaded area might have few individuals and a more exposed area might have many individuals

Uncontrollable variables

Certain additional factors that are difficult to account for can affect the distribution of a species, for example beneficial moisture may be more prevalent in shaded areas when investigating light intensity

Photosynthesis

Photosynthetic organisms such as plants or algae are the producers of biomass for life on Earth

Biomass

The mass of living organisms in an ecosystem which is composed of all of the molecules an organism synthesises or gains from the consumption of other organisms

Food chain

A diagram to show simple relationships in an ecosystem with a focus on the food sources of organisms, an arrow shows the transfer of energy or biomass along the food chain

Food web

Multiple interconnected food chains that better represent the relationships of organisms in an ecosystem

Producer

A plant or algal species that starts a food chain by synthesising molecules, specifically glucose that is produced via photosynthesis

Consumer

An organism that eats another organism to gain molecules that can be used for energy and important biological processes

Primary consumer

An animal that eats producers such as plants or algae

Secondary consumer

An animal that eats primary consumers

Tertiary consumer

An animal that eats secondary consumers

Herbivore

An animal that eats plants, can also be referred to as a primary consumer

Carnivore

An animal that eats other animals, can be a secondary or tertiary consumer

Omnivore

An opportunistic animal that can eat both plants or other animals

Detritivore

A type of decomposer that feeds on dead organic material such as plant detritus in the form of fallen leaves

Decomposer

An organism responsible for the decay and breakdown of other dead organisms, so that important nutrients can be recycled

Prey

An animal that is eaten by another animal called a predator

Predator

A consumer that kills or eats other animals known as prey

Apex predator

An animal at the top of a food chain or web, the apex predator has no predators of its own

Distribution and abundance of species

Can be measured using a range of experimental methods using transects and quadrats

Predator-prey relationship

The interaction between an organism that eats another organism and the consequent effect one species has on the other

Trophic levels

The different levels of organisms in a food chain, each level is represented by a specific number

Food web

A network of complex relationships formed by multiple food chains consisting of organisms that interact in an ecosystem

Ecosystem

A system formed by the interaction of living organisms with their physical environment

Producer

An organism such as a plant that can make its own food and biomass using energy from solar radiation

Solar radiation

The source of energy for all organisms in a food chain, plants use the energy for photosynthesis which can be passed on to other organisms when a plant is eaten

Consumer

An organism that obtains energy and biomass by feeding on other organisms, can be a primary, secondary, tertiary or even quaternary consumer

Trophic level 1

Plants and algae occupy this trophic level, they make their own food via photosynthesis and are called producers

Trophic level 2

Herbivores occupy this trophic level, they eat plants or algae and are called primary consumers

Trophic level 3

Carnivorous predators that eat prey in the form of herbivores are called secondary consumers, they occupy this trophic level

Trophic level 4

Carnivorous predators that eat prey in the form of other carnivores are called tertiary consumers, they occupy this trophic level

Apex predator

A carnivorous animal at the top of a food chain, the apex predator has no predators of its own

Pyramids of number

A pyramid that is constructed to represent the number of individuals in each level of a food chain, trophic level 1 is at the bottom of the pyramid

Pyramids of biomass

A pyramid that is constructed to represent the relative amount of biomass in each level of a food chain, trophic level 1 is at the bottom of the pyramid

Reasons for loss of biomass in a food chain

Not all ingested material is absorbed and some is egested as faeces, some absorbed material is lost as waste such as carbon dioxide and water during respiration or water and urea in urine

Energy in producers and consumers

Plants and algae only transfer about 1% of energy from solar radiation, from this available energy only about 10% is transferred to each consecutive trophic level

Reasons for 90% loss of energy between trophic levels

Organisms require the energy they get from food for cell repair and growth, movement, heat and metabolic processes, a lot of energy is also lost via waste materials and respiration

Efficiency of energy transfer calculation

Percentage efficiency transfer = (Energy transferred to the next level/energy available from the previous level) x 100

Efficiency of biomass transfer calculation

Percentage efficiency transfer = (Biomass transferred to the next level/biomass available at the previous level) x 100

Reasons for numbers of organisms

Less biomass and energy is available at higher trophic levels, which explains why there are far fewer individual apex predators than individuals at lower trophic levels

Advantages of each pyramid type

Pyramid of number can visualise the abundance of organisms at each trophic levels, pyramids of biomass show the transfer of mass and size of organisms which better represents the relationships in ecosystems

Decomposition

Animals, plants and waste products are typically broken down by microorganisms, assuming the conditions for decay are available

Digestion of nutrients during decomposition

Microorganisms secrete digestive enzymes to their surroundings, extracellular digestion occurs where small soluble products are produced that can be absorbed

Detritus

Dead particulate organic material such as leaf litter that is mixed with soil

Humus

Rich, dark organic material formed by decay of vegetable matter, essential for the fertility of soil