Topic 4: Ecology And The Environment

Question 1

Population in ecosystems

Answer 1

An individual is part of a species, but lives in its habitat within a population. Many different populations interact in the same habitat, creating a community. The populations are often dependent on each othr. An ecosystem is the interaction of a community with non-living (abiotic) parts of the environment. Organsisms are adapted to live in the conditions of their environment.

Question 2

Practical: investigate the population size of an organism in two different areas using quadrats

Answer 2

· Quadrats are used to study ecology, as they make it easier to estimate distribution and abundance of organisms within a large area by looking at a few smaller representative samples
· A transect is a defined area where the samples will be taken and is used to estimate the number of the organism across the whole area, such as across a whole field
· The quadrats are placed along the transect and the amount of the chosen organism is counted
· The quadrats can also be randomly placed across the whole area, rather than using a transect
· Alternatively, percentage cover can also be estimated but this is subjective and ess accurate than counting which gives a quantitative value
· The accuracy of the quadrat estimations can b improved by doing some samples, repeat testing or completing the sampling over larger transects

Question 3

Biodiversity

Answer 3

Biodiversity is a measure of the range of species living within an ecosystem

Question 4

Practical: investigate the distribution of organisms in their habitats and measure biodiversity using quadrats

Answer 4

· You use quadrats to count the populations of diffent species
· The reliability is improved by placing the quadrat randomly (e.g. using a random generator), using the same size quadrats each time, increasing the number of samples taken in each area

Question 5

Abiotic (non-living) Factor: Light intensity

Answer 5

Light is required for photosynthesis and the rate of photosynthesis affects the rate at which the plants grows. Also, plants can be food sources or shelter for many organisms

Question 6

Abiotic (non-living) Factor: Temperature

Answer 6

Temperature affects the rate of photosynthesis

Question 7

Abiotic (non-living) Factor: Moisture levels

Answer 7

Both plants and animals need water to survive

Question 8

Abiotic (non-living) Factor: Soil pH and mineral content

Answer 8

Soil pH affects the rate of decay and therefore how fast mineral ions return to soil (which are then taken up by other plants). Different species of plants thrive in different nutrient concentration levels

Question 9

Biotic (living) Factor: Food availability

Answer 9

More food means organisms can bread more successfully and therefore the population can increase in numbers

Question 10

Biotic (living) Factor: New pathogens

Answer 10

When a new pathogen arises the population has no resistance to it so they can be wiped out quickly

Question 11

Biotic (living) Factor: Competition

Answer 11

If one species is better adapted to the environment than another, then it will outcompete it until the numbers of lesser adapted species are insufficient to breed

Question 12

Trophic levels

Answer 12

Trophic levels are the feeding levels in a food chain

Question 13

Producers

Answer 13

Organisms that make their own food by photosynthesis, e.g. plants and algae

Question 14

Primary consumers

Answer 14

Herbivores that only eat plants (producers)

Question 15

Secondary consumers

Answer 15

Carnivores that eat primary consumers

Question 16

Tertiary consumers

Answer 16

Carnivores that eat secondary consumers. They have no predators and so are called the apex predators

Question 17

Decomposers

Answer 17

Bacteria and fungi that break down dead animal’s body and waste for energy, using enzymes

Question 18

Food chains

Answer 18

They show the feeding relationships between organisms. They are organised by trophic level

Question 19

Food webs

Answer 19

They are a collecton of different food chains to show all the organisms in the habitat, showing interdependence and therefore how population number changes can affect the entire ecosystem

Question 20

Pyramids of numbers

Answer 20

· Shows the population of each organism at each trophic level of food chain
· Producers are at the bottom and bars ususally get smaller the further up you go
· However, if the producer is a large plant, e.g. a tree, the size of the bar is very small as one tree can feed many insects (primary consumers)

Question 21

Pyramids of biomass

Answer 21

Pyramids of biomass show the relative biomass at each trophic level.
· It shows the relative dry mass of material at each level
· There are less biomass as you move up the trophic levels
· Not all the food consumed by an animal is converted into biomass - this means the biomass of the organism in the level above another will always be higher, as not all the organism can be consumed and converted into biomass