The Organism in the Environment (Edexcel IGCSE Science (Double Award): Biology): Flashcards
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Define population.
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Cards in this collection (42)
Define population.
A group of organisms of the same species living in the same place at the same time.
Define community.
All of the populations living in the same area at the same time.
Define habitat.
The place where an organism lives.
Define ecosystem.
All the biotic factors and all the abiotic factors that interact within an area at one time.
What is the difference between a biotic and an abiotic factor?
Biotic — the living components, such as plants and animals
Abiotic — the non-living components, such as light intensity, mineral ions and water availability
Why can removing one species affect a whole community?
Because within a community each species depends on others for food, shelter, pollination and seed dispersal.
Give an example of a small and a large ecosystem.
Small — a garden pond
Large — the whole of Antarctica
Name four species that might share a woodland habitat.
Badgers
Deer
Oak trees
Ants
All the populations living in the same area at the same time make up a ＿＿＿＿＿＿＿＿.
All the populations living in the same area at the same time make up a community.
Light intensity and water availability are examples of ＿＿＿＿＿＿＿＿ factors.
Light intensity and water availability are examples of abiotic factors.
True or False?
A population contains organisms of several different species.
False.
A population is one species only. All the populations together make up the community.
True or False?
An ecosystem includes both living and non-living components.
True.
An ecosystem is all the biotic and abiotic factors interacting within an area.
Define quadrat.
A square frame of wood or wire, placed on the ground so the organisms within it can be recorded.
Common sizes are 0.25 m2 and 1 m2.
What two measures of abundance can a quadrat record?
The number of individuals of a single species
Percentage cover — roughly what percentage of the quadrat's area a species occupies
When is percentage cover used instead of counting individuals?
When it is difficult to count individual plants, for example with grass or moss.
Why must quadrats be placed using random numbers?
To make the sampling random, so the results are representative of the whole survey area rather than biased.
What is ecology?
The branch of biology that studies species distribution and abundance, interactions between species, and their interactions with the abiotic environment.
Name four biotic factors that influence species abundance.
Competition
Predator-prey relationships
Interactions within the food chain or web
Disease
Name six abiotic factors that influence species abundance.
Light intensity
Mineral availability
Water availability
pH
Temperature
Salinity
Give one limitation of quadrat sampling and its solution.
It is easy to miss individual organisms, especially if covered by another species.
Use a pencil or stick to carefully move leaves aside and check underneath.
How can difficulty identifying species be overcome?
Use a species key.
What can you do once averages from both survey areas are calculated?
Compare the abundance of the species in each of the two areas.
A ＿＿＿＿＿＿＿＿ is a square frame placed on the ground to sample the organisms inside it.
A quadrat is a square frame placed on the ground to sample the organisms inside it.
For plants that are hard to count individually, record the ＿＿＿＿＿＿＿＿ cover instead.
For plants that are hard to count individually, record the percentage cover instead.
True or False?
One quadrat is enough to estimate a population in an area.
False.
Many quadrats must be placed randomly and a mean calculated, so that the sample represents the whole area.
True or False?
Quadrats are mostly used to estimate the abundance of plants.
True.
Plant species are commonly studied with quadrats because they do not move.
Define abiotic factor.
A non-living factor within an environment — for example temperature, light intensity and wind speed.
Define biotic factor.
A living factor in the environment — for example competition, predation and disease.
How does light intensity affect a community?
Light is needed for photosynthesis. At low light levels plants grow more slowly and produce less food for herbivores, which affects the whole food chain.
How does temperature affect population size and distribution?
It affects the rate of enzyme-controlled reactions. If it is too hot or too cold, enzymes work inefficiently, reducing survival and reproduction rates.
How does water availability affect an ecosystem?
Water is essential for life, so the amount available determines which plants and animals can survive there — cacti in deserts, amphibians only in moist habitats.
How does soil quality affect a community?
Soil provides water, minerals and anchorage. Poor or acidic soils limit plant growth, which affects the whole food web — heather grows on acidic moorland where grasses do not.
How does oxygen availability affect aquatic habitats?
Some animals, such as fish, need high oxygen concentrations.
In warm, stagnant ponds oxygen levels drop, so animals die or migrate.
Why are lichens used as indicators of clean air?
They are sensitive to air pollution, such as sulfur dioxide, so few lichens are found where air pollution is high.
How does food availability affect population size?
More food means a higher chance of surviving and reproducing, so populations increase.
When food is scarce, only the best-adapted organisms survive and reproduce.
How can a new predator disrupt an ecosystem?
It upsets the balance between predator and prey, causing prey populations to decline — as red foxes introduced to Australia did to native mammals and birds.
Why can a new pathogen devastate a population?
The populations there may have no immunity or resistance to it, so their numbers fall sharply or they are wiped out — as with ash dieback in European ash trees.
How have grey squirrels affected UK red squirrels?
Grey squirrels outcompete them for food and nesting sites, and also carry a virus that red squirrels are not resistant to, so red squirrel numbers fall.
Temperature, light intensity and wind speed are all examples of ＿＿＿＿＿＿＿＿ factors.
Temperature, light intensity and wind speed are all examples of abiotic factors.
Competition, predation and disease are all examples of ＿＿＿＿＿＿＿＿ factors.
Competition, predation and disease are all examples of biotic factors.
True or False?
If two species compete, the better-adapted one will outcompete the other.
True.
The less well-adapted species may decline or even become extinct if its population falls too low to breed successfully.
True or False?
Pollution is an abiotic factor.
True.
High pollution levels damage habitats and kill sensitive species, so fewer species can survive there.
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