The Organism in the Environment Flashcards
All 26 cards in this deck
What is a population?
All the organisms of one species living in a habitat at one time.
What is a community?
All the populations of different species living in the same habitat.
What is an ecosystem?
A community of organisms together with the abiotic (non-living) parts of their environment, interacting with each other.
List the levels of ecological organisation in order, from smallest to largest.
Individual organism → population → community → ecosystem.
Name four abiotic factors that affect communities.
Temperature, light, water and pollutants.
Name the two biotic factors named in the specification that affect communities.
Competition and predation.
True or false? Light intensity is a biotic factor.
False. Light is an abiotic (non-living) factor; biotic factors are living, such as competition and predation.
How does a rise in predator numbers affect the prey population, and what happens next?
The prey population falls; the predator population then falls because there is less food, letting prey numbers recover.
Why can a non-indigenous plant come to cover a whole lake? Give two reasons.
Conditions are suitable for its growth/photosynthesis so it grows and reproduces, and it outcompetes the natural plants; also no natural herbivores eat it.
What is interdependence in a community?
Species depend on each other for things such as food, shelter, pollination and seed dispersal, so a change in one population affects others.
Hedgehogs eat slugs and earthworms. State one effect on the earthworm population of using slug pellets to kill all the slugs.
The earthworm population decreases, because more earthworms are eaten by the hedgehogs.
True or false? Removing one species from a community only affects the species that eats it.
False. Because species are interdependent, removing one species can have knock-on effects throughout the community.
What is parasitism?
A relationship where the parasite gains and the host is harmed.
What is mutualism?
A relationship between two species in which both organisms benefit.
Describe the feeding relationship between mistletoe and the tree it grows on.
The tree is the host; the mistletoe gains nutrients/water from the tree and the tree is damaged by it.
Bacteria in the root nodules of a leguminous plant give it nitrogen compounds, and the plant gives the bacteria sugars. What is this relationship called?
Mutualism.
True or false? Fleas living on a dog is an example of mutualism.
False. It is parasitism — the flea gains food (blood) and the dog is harmed.
How is the size of a population estimated from quadrat samples?
population size = mean number of organisms per m² (from the quadrats) × total area of the habitat (m²)
How is randomness achieved when choosing where to place quadrats?
Use a random number generator to give random coordinates for the quadrat positions.
What is a belt transect used to investigate?
How the distribution of organisms changes across a habitat along an abiotic gradient, e.g. light intensity away from a wood.
What are the steps to carry out a belt transect?
e.g. nettle growth as light intensity changes away from a wood
- Lay a tape measure/rope in a line across the habitat.
- Place a quadrat at measured intervals along it and record the nettles in each.
- Measure light intensity at each distance with a light meter.
Name the instruments used to measure light intensity, temperature and soil water in a habitat.
Light/lux meter, thermometer and water (moisture) meter or sensor.
True or false? Taking more quadrat samples makes the estimate of population size more reliable.
True. A larger sample size reduces the effect of anomalies and makes the mean more representative.
What is competition between organisms?
When organisms of the same or different species need the same limited resources (e.g. food, water, light or space), so not all of them get enough.
How are bees and flowering plants an example of mutualism?
The bees get food (nectar) from the flowers, and as they move between flowers they carry pollen, pollinating the plants so they can reproduce.
In quadrat sampling, what is percentage cover and when is it used?
An estimate of the percentage of the quadrat's area covered by one species. It is used when individuals are hard to count, e.g. grass or moss.