1
Q
ecosystem
A
- a unit containing the community of organisms and their environment, interacting together
- consists of a living/biotic component (the communities) and a non-living/abiotic component (the environment in which the communities live)
2
Q
population
A
a group of organisms of one species, living and interacting in the same area at the same time
3
Q
community
A
all of the populations of different species interacting with each other in an ecosystem
4
Q
habitat
A
the place where organisms live
5
Q
examples of abiotic factors
A
- availability of oxygen
- availability of water
- light intensity
- pH (of water or soil)
- pollution
- temperature
- mineral ions
6
Q
effects of changing abiotic factors
A
- may affect the numbers of individuals in populations in the community which can affect the food web
- changes can also have positive effects e.g. an increase in temperature or light intensity can encourage plant growth which can provide more food for herbivores, or more camouflage, or sites for breeding
7
Q
examples of biotic factors
A
- competition
- disease
- food supply
- predation
8
Q
types of competition
A
- intraspecific: competition between organisms of the same species for resources (e.g. food, territory, mate)
- interspecific: competition between organisms of different species for resources
- intraspecific competition has a greater impact on the population size than interspecific
9
Q
Relationship between prey and predator numbers
A
- the breeding rate of the population may not be enough to replace those eaten by predators, so the number of individuals in the population will drop
- As the number of prey increases, the number of predators increases
- As the number of predators increase, the number of prey decreases so there is less food for the predators. The number of predators then decreases, and so on.
- There is always a time lag between changes in prey numbers and changes in predator numbers
10
Q
pollution
A
- the introduction of raw sewage into a water system which can reduce the oxygen available to fish
- acid rain, caused by combustion of fossil fuels such as coal, kills populations of trees and reduces populations of trout in lakes
11
Q
climate change
A
- Increases in water temp due to global warming have negative effects on coral. As corals bleach and die, food chains are destroyed so the whole community in that ecosystem is destabilised
- As water warms up, the solubility of oxygen in it decreases which is a problem as most species of aquatic animals rely on oxygen for aerobic respiration
12
Q
phases of growth for micro-organisms
A
- Lag phase: population is very small and takes time to acclimatise to a new environment, become mature and start reproducing
- Log/exponential phase: no limiting factors. rapid breeding in the population, resulting in significant increases in numbers, far more births than deaths
- Stationary phase: shortage of food and build-up of toxic materials in the environment start to have an effect, slowing down population growth, gets to the point where no. of deaths = no. of births, so line flattens
- Death phase: no. of deaths>no. of births so population numbers start to decrease, may be due to lack of food, accumulation of toxic materials, disease spreading through the population, or an influx of predators
13
Q
factors that cause a rise in population numbers for humans
A
- more births than deaths
- more efficient food production
- lower infant mortality rates
- better control of diseases
14
Q
mutualism
A
a close relationship between two organisms of different species where both organisms benefit
15
Q
parasitism
A
-a relationship in which the parasite benefits, whilst the host is harmed
16
Q
survival of the fittest + example
A
- Through intraspecific competition, stronger individuals in a population tend to survive and breed, passing their favourable genes to the next generation
- example: In Britain, the red squirrel is in decline because of interspecific competition with grey squirrels. Grey squirrels are more successful in forcing red squirrels out of their natural habitats because they are bigger, have a greater range of food sources and spread a disease which kills red squirrels but is not usually lethal to greys.
17
Q
fates of light
A
- 1% is absorbed by photosynthetic plants to make their food
- some light is reflected
- some light is used to evaporate water from leaves (transpiration)
- some light warms up the soil, plants and air
18
Q
photosynthesis
A
- carried out by green plants and some types of bacteria
- Photosynthesis is a process whereby plants absorb light energy, using pigments such as chlorophyll, and convert it into chemical energy – stored in molecules e.g. carbohydrates, fats and proteins
- The food produced and built up in a plant is known as its biomass
- carbon dioxide + water -> oxygen + glucose
19
Q
food chain parts
A
- producers- photosynthetic plants
- primary consumers - herbivores
- secondary consumers - carnivores
20
Q
food chain definition
A
-A food chain shows the transfer of energy between one organism and the next, beginning with a producer
21
Q
food webs
A
- composed of many interlinked food chains
- they are more accurate because in reality each organism eats and is eaten by a variety of other organisms
22
Q
energy loss
A
-only 10% of energy is passed from one organism to another
Energy can:
-be lost due to heat (during respiration, movement, metabolism),
-remain in undigested food that passes through the organism and is removed in faeces
-stored in undigestible material (e.g. horns, fur) that is not eaten by the next organism
23
Q
uses for sugar produced by photosynthesis
A
- respiration (can be broken down again to provide energy)
- storage (can be converted to starch which is a storage sugar)
- structure (can be converted to cellulose, the main component of plant cell walls)
- metabolic pathways (sugars can enter other metabolic pathways that convert it to proteins/fats)
24
Q
decomposition
A
- When organisms die, they provide food for detritus feeders (e.g. worms, woodlice and microorganisms)
- Decomposition is the process by which bacteria and fungi break dead organisms into their simple compounds (CO2 and nitrate)
- Bacteria/fungi secrete digestive enzymes out of their cells into the soil or dead organism
- Some of the products are absorbed by the bacteria/fungi
25
deforestation
Deforestation has a detrimental effect on the amount of carbon dioxide in the air because:
1. there are fewer trees photosynthesising, so less carbon dioxide is removed from the air
2. when the trees are cut down, the small branches and foliage are burned, adding more carbon dioxide back into the air through the process of combustion
26
the water cycle
Transpiration – plants release water vapour into the atmosphere, mainly through stomata in the leaves. The water evaporates inside the leaf before it is released
Evaporation – occurs from the surface of bodies of water
Condensation – water vapour in the atmosphere condenses to form clouds
Precipitation – water in the clouds forms rain, snow, etc. which falls to the land and drains into water systems
Osmosis – the process used by plant roots, bacteria and other organisms to take up water
Excretion – water is lost from animals in the form of sweat, exhaled air, urine and faeces
27
the carbon cycle
- Photosynthesis - plants absorb CO2 from the atmosphere
- Feeding - animals eat plants which contain carbon in many forms
- Decomposition - complex carbon compounds in dead organisms, urine and faeces are broken down into simpler carbon compounds by bacteria or fungi
- Respiration - living organisms (plants, animals and decomposers) respire, releasing CO2 into the atmosphere
28
nitrification process
ammonium compounds -> nitrites -> nitrates
BMAT Biology
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