Unit 3A Flashcards
Habitat
The place where an organism is found.
Community
All the living organisms in a habitat - plants, animals and micro-organisms.
Ecosystem
Habitat + community + the interactions between them.
Abiotic factors
The non-living physical features of a habitat. eg. temperature, pH, moisture levels.
They can be measured using instruments eg. light meters, pH and temperature probes.
They affect the distribution of living organisms in a habitat.
Sampling techniques
Used to investigate the living organisms present in a habitat.
eg. pitfall traps to measure the woodlouse population, quadrats for plant species.
Population
Organisms that belong to the same species and live in the same area.
Pitfall trap
Used to estimate the population of ground-dwelling invertebrates such as woodlice.
A cup with steep sides is buried in the ground, and the entrance is disguised to deter predators.
The invertebrates are captured when they fall in and can’t escape.
Quadrat
A sampling square used to estimate abundance of organisms that don’t move eg. plants.
Transect
A line crossing a habitat from one set of conditions to another eg. light to shade or down a slope.
Quadrat samples and measurements of abiotic factors are taken at regular intervals along the line.
This shows how distribution of organisms changes across the habitat.
Abundance
How many organisms there are in a sample area.
It can be measured using a quadrat, by counting how many squares each species appears in.
eg if it is found in 7/25 squares, the abundance is 7 (regardless of how many individual organisms there are)
Interdependence
Describes how the members of a community depend on each other.
Examples include food, shelter, pollination, seed dispersal, nutrient cycling and exchange of gases.
Pollination
Transfer of the male gamete (pollen) to the stigma of another flower, so that it can be fertilised.
Insect pollinated flowers depend on insects to transfer the pollen.
Insects gain nectar and pollen as a food reward.
Seed dispersal
Seeds are contained inside fruits (modified ovary walls) that are used to spread the seeds.
When birds eat berries they gain food, and they spread the seeds of the plant.
When burrs hook onto animal fur, the plant is depending on the animal to spread its seeds.
Shelter
Animals can provide shelter for other animals eg. anemones/clown fish.
Plants provide shelter, habitats and building materials for animals and birds eg. swans nest in reeds, birds nest in trees.
Decomposers
Bacteria and fungi.
Essential for nutrient cycling, as they break down dead material and return nitrates to the soil.
Gas exchange
Plants absorb carbon dioxide for photosynthesis and release oxygen, which is used for respiration by both animals and plants.
Biotic factors
Interactions between different species in a habitat.
Interactions include food availability, predation, disease and competition.
Food availability
Determines the abundance (number) and distribution of species.
Food is scarce in some habitats, and population numbers are low eg. Arctic
Food is abundant in others, eg. mudflats, supporting large numbers of organisms.
Predation
Predators hunt prey animals for food.
Predators and prey are interdependent, with the numbers of predators affecting the number of prey, and vice versa.