3.11 - Competition & Interdependence Flashcards
State the 4 different levels of organisation in ecosystems and their definitions
- Individual - A single organism.
- Population - All the organisms of one species in a habitat.
- Community - All the organisms (different species) living in a habitat.
- Ecosystem - A community of organisms along with all the non-living (abiotic) conditions.
What do plants need in ecosystems?
Plants need light, space, water, minerals from the soil, seed dispersers (e.g. animals that eat fruit and spread the seeds in their droppings) and pollinators (e.g. bees)
What do animals need in ecosystems?
Animals need space (territory), shelter, food, water and mates
What is the size of a population limited by? (2)
- Predation
- Competition for resources
The environment in which plants and animals live changes all the time. What are these changes caused by?
Abiotic (non-living) and biotic (living) factors
How do abiotic factors affect communities? (2 - detailed)
- Environmental conditions - e.g. the distribution of bird species in Germany appears to be changing because of a rise in average temperature. Other environmental conditions that affect the abundance and distribution of organisms include light intensity (plants only), moisture level and soil pH.
- Toxic chemicals - e.g. chemical pesticides or fertilisers. Pesticides can build up in food chains through bioaccumulation - this is where, at each stage of the food chain, concentration of the pesticide increases, so organisms at the top of the chain receive a toxic dose. Excess fertilisers released into lakes and ponds cause increased growth of algae. This is called eutrophication. The algae block sunlight from plants, which die. Microorganisms feeding on the dead plants use up oxygen in the water, leading to the death of other organisms.
How do biotic factors affect communities? (3)
- Availability of food - e.g. in a bumper year for berries, the population of blackbirds might increase because they’ll be enough food for all of them, so they’re more likely to survive and reproduce.
- Number of predators - e.g. if the number of lions (predator) decreases then the number of gazelles (prey) might increase because fewer of them will be eaten by the lions.
- Presence of pathogens - e.g. if a new pathogen was introduced into the community then populations may decrease due to illness.
What is interdependence?
The idea that all species depend on other species in some way.
How can interdependence be shown?
Through using a food web
In ecology, what is a ‘community’?
All the populations of different species that live together in a habitat.
An _________ is the interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment.
ecosystem
Give three resources that animals compete for. (3m)
Food (1), Water (1), Mates (1), Territory (1)
Give three resources that plants compete for. (3m)
Mineral ions (1), Water (1), Light (1), Space (1)
Describe the steps of how to use a quadrat to study the distribution of small organisms (6)
1) Place a 1m quadrat on the ground at a random point within the first sample area. E.g. divide the area into a grid and use a random number generator to pick coordinates. Otherwise, if all your samples are in one spot and everywhere else is different, the results you get won’t be representative of the whole sample area.
2) Count all the organisms you’re interested in within the quadratic.
3) Repeat steps 1 and 2 many times.
4) Work out the mean number of organisms per quadratic within the first sample area. (mean = total number of organisms/number of quadrats)
5) Repeat steps 1 to 4 in the second sample area.
6) Finally compare the two means. E.g. you might find 2 daisies per m squared in the shade, and 22 daisies per m squared in an open field.
