Topic 4: Ecology And The Environment Flashcards
Population in ecosystems
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.
Practical: investigate the population size of an organism in two different areas using quadrats
· 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
Biodiversity
Biodiversity is a measure of the range of species living within an ecosystem
Practical: investigate the distribution of organisms in their habitats and measure biodiversity using quadrats
· 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
Abiotic (non-living) Factor: Light intensity
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
Abiotic (non-living) Factor: Temperature
Temperature affects the rate of photosynthesis
Abiotic (non-living) Factor: Moisture levels
Both plants and animals need water to survive
Abiotic (non-living) Factor: Soil pH and mineral content
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
Biotic (living) Factor: Food availability
More food means organisms can bread more successfully and therefore the population can increase in numbers
Biotic (living) Factor: New pathogens
When a new pathogen arises the population has no resistance to it so they can be wiped out quickly
Biotic (living) Factor: Competition
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
Trophic levels
Trophic levels are the feeding levels in a food chain
Producers
Organisms that make their own food by photosynthesis, e.g. plants and algae
Primary consumers
Herbivores that only eat plants (producers)
Secondary consumers
Carnivores that eat primary consumers
Tertiary consumers
Carnivores that eat secondary consumers. They have no predators and so are called the apex predators
Decomposers
Bacteria and fungi that break down dead animal’s body and waste for energy, using enzymes
Food chains
They show the feeding relationships between organisms. They are organised by trophic level
Food webs
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
Pyramids of numbers
· 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)
Pyramids of biomass
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
