Unit 3.2: Distribution of organisms Flashcards
Describe what a biotic factors.
Factors that effect living organisms
Give examples of biotic factors.
Predation Disease Food competition Space competition Grazing
Describe the effect of the lack of predation on prey populations.
Removing predators increases preys population
Describe the effect of increased predation on prey populations.
If there’s more predators prey would decreases
What happens in low levels of grazing?
Biodiversity decreases because fast-growing vigorous plants will grow and block out light from smaller, low growing plants which stop them from photosynthesising.
What happens in high levels of grazing?
Biodiversity increases because it keeps fats growing vigorous plants in check so all plants get light and photosynthesis
What happens in very high levels of grazing?
Biodiversity decreases because all plants except low ones get eaten
Describe what an abiotic factor is.
Factors that effect non-living organisms
Give examples of abiotic factors.
pH
Temperature
Moisture
Light intensity
Why does increasing light intensity increases plant growth?
The more light there is available the more plants photosynthesis and thus thrive
Why do low levels of water decrease plant growth?
There is not enough water for the plants to thrive and stay healthy so that tends to make them die
How do you measure light intensity?
Using a light meter
What errors can happen with using a light meter and how do you reduce it?
You can end up blocking the sensor so ensure the sensor is facing towards the light
How do you measure soil moisture?
Using a moisture meter
What errors can happen with using a moisture meter and how do you reduce it?
If the probe is dirty so after every use make sure to clean the probe
How do you measure pH?
By using a pH meter
What errors can happen with using a pH meter and how do you reduce it?
If the probe is dirty so after every use clean it
How do you measure temperature?
By using a thermometer
What errors can happen with using a thermometer and how do you reduce it?
By using a dirty thermometer or reading it immediately after placing it so clean it after every use and let it sit for a while before taking measurements
When measuring abiotic factors what is required to ensure a representative sample is taken?
By repeating it many times
What are quadrats used to measure the abundance of?
Plants and slow living organisms
How do you sample plant abundance using a quadrat?
Place randomly and count the number of squares not number of organisms
What errors can occur in quadrat sampling?
Not placing randomly
Bad counting
Lack of knowledge with species
Describe the step required in quadrat sampling to ensure representative sample is taken.
If more than half is in the quadrat then it counts
State the type of organisms that pitfall traps are used to measure the abundance of.
Ground living invertebrates
Describe how to sample using a pitfall trap.
Level with soil
Put drainage holes
Cover with leaves
describe sources of error in pitfall traps.
Not levelling the pot with the ground so invertebrates dont fall
Birds taking the insects before they are counted
Leaving the trap for too long so predation of some organisms by other invertebrates.
Describe the step required in pitfall traps to ensure a representative sample is taken.
Repeat with other pots for representative samples.
State 5 human influences that result in a decrease in biodiversity.
Air pollution Water pollution Habitat destruction Desertification Over-fishing
How does air pollution affect biodiversity?
the production of gases such as CO2, SO2 and nitrous oxide in high concentrations can kill many species
How does water pollution affect biodiversity?
The release of sewage into waterways or oils spills at sea are the main causes. Oil destroys the insulating ability of fur-bearing animals and how well birds feathers repel water. Without that birds and mammals die from hypothermia. Plus raw sewage reduces oxygen levels killing many species.
How does habitat destruction affect biodiversity?
Clearing space for roads, cities or agriculture many species living in these areas lose their habitats.
How does desertification affect biodiversity?
Fertile land becomes desert, resulting in drought. many species cannot adapt to living in desert conditions so quickly so they die
How does overfishing affect biodiversity?
Fish stocks become reduced to below acceptable levels resulting in resource depletion which reduces biological growth rates.
Define endangered.
Certain species are at risk of becoming extinct
Define indicator species.
If species are present or absent in an environment it indicates the quantity levels of pollution
What are lichens used to indicate?
Air pollution
How can mayfly larvae be used as an indicator?
They cannot survive in polluted areas so their absence means that there is pollution in that area.
