The Organism in the Environment Flashcards

All 31 cards in this deck

What is a population?

All the organisms of one species living in the same habitat at the same time.

What is a community?

All the populations of different species living together 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.

What is a habitat?

The place where an organism lives.

Put these levels of organisation in order, smallest first: community, ecosystem, organism, population.

Organism → population → community → ecosystem.

True or false? A community includes the non-living parts of the environment.

False. A community is only the living organisms; an ecosystem is the community plus the abiotic factors.

What is an abiotic factor?

A non-living factor that affects organisms in a habitat.
e.g. temperature, light intensity, water availability, pollutants

What is a biotic factor?

A living factor that affects organisms in a habitat.
e.g. competition, predation, disease

What do plants in a community compete with each other for?

Light, water, space and mineral ions in the soil.

How does a fall in light intensity affect the number of small plants growing in a woodland?

The number of plants decreases, because they cannot photosynthesise enough to grow.

What happens to a prey population when the predator population increases?

The prey population falls; the predators then have less food, so their numbers fall too.

True or false? Pollutants are biotic factors.

False. Pollutants are abiotic factors, and they can reduce the size of a population or change where a species is found.

What is interdependence?

The way species in a community depend on one another for things such as food, shelter, pollination and seed dispersal.

What can happen to a community if one species is removed?
e.g. a plant species dies out

Species that depend on it are affected — the herbivores that eat the plant decrease, and the predators of those herbivores then decrease too.

What do many flowering plants depend on insects for?

Pollination, so that seeds and fruits can be produced.

True or false? Removing one species from a community only affects the species that eat it.

False. Because species are interdependent, there are knock-on effects on many other species in the community.

What is parasitism?

A relationship in which a parasite lives on or in a host, gaining a benefit such as food, while the host is harmed.

Name two examples of parasites.

Fleas, head lice, tapeworms or mistletoe.

What is mutualism?

A relationship between two species in which both organisms benefit.

In the mutualism between a legume plant and nitrogen-fixing bacteria in its root nodules, what does each partner gain?

The bacteria gain sugars from the plant; the plant gains nitrogen compounds (nitrates/amino acids).

In the mutualism between cleaner fish and larger fish, what does each partner gain?

The cleaner fish gain food (parasites and dead skin); the larger fish have their parasites removed and stay healthy.

True or false? A parasite usually kills its host quickly.

False. The parasite depends on the host for food and shelter, so it harms the host but usually does not kill it quickly.

What is biodiversity?

The variety of different species living in a habitat or ecosystem.

True or false? A community with high biodiversity is usually more stable than one with low biodiversity.

True. Species are less dependent on any one other species, so the community copes better if one species changes in number.

When sampling with quadrats, what is recorded to compare the biodiversity of two habitats?

The number of different species found in each habitat, and how abundant each one is.

What are the steps to estimate the total number of a species in an area using quadrat data?
e.g. counts of 3, 4, 5 and 4 daisies in four $1\text{ m}^2$ quadrats in a $200\text{ m}^2$ field

1. Place quadrats randomly and count the organisms in each: 3, 4, 5, 4.
2. Calculate the mean per quadrat: $16 \div 4 = 4$ per $1\text{ m}^2$.
3. Multiply the mean by the total area: $4 \times 200 = 800$ daisies.

What are the steps to place quadrats randomly in a field?
e.g. sampling daisies in a grassy field

1. Lay two tape measures at right angles to make a grid.
2. Use a random number generator to get pairs of coordinates.
3. Place the quadrat at each coordinate and count the daisies — random placement avoids bias and gives a representative sample.

What are the steps to carry out a belt transect?
e.g. how seaweed changes up a rocky shore

1. Lay a tape measure in a straight line along the environmental gradient (low shore to high shore).
2. Place a quadrat at regular intervals along the tape, e.g. every $2\text{ m}$.
3. Record the abundance of each species in every quadrat, plus abiotic factors such as light or water.

What are the steps to estimate the percentage cover of a species in a quadrat?
e.g. moss in a quadrat divided into 100 small squares

1. Count the small squares the species covers, counting a square if it is more than half covered: 35 squares.
2. Percentage cover $= \frac{35}{100} \times 100 = 35\%$.

True or false? The type of food used to bait a pitfall trap can affect the number of different invertebrates caught.

True. One type of food may attract only some invertebrates, so the sample is not representative.

What does a kite diagram show?

How the abundance of each species changes with distance along a transect.