section 4: Ecology and the environment Flashcards
definitions: population, community, habitat and ecosystem
-population: all the organisms of one species in a habitat (e.g: a rocky shore or a field)
-community: all the different species in a habitat
-habitat: the place where an organism lives
-ecosystem: all the organisms living in a particular area and all the non-living (abiotic) conditions (e.g: temperature, climate, soil-type)
practical: investigate the population size of an organism in two different areas using quadrats
-> a quadrat is a square frame enclosing a known area, e.g. 1m^2. To compare the population size of an organism in two sample areas just follow these simple steps:
1) Place a 1 m^2 quadrat on the ground at a random point within the first sample area. You could this by dividing the sample area into a grid and using a random number generator pick to pick coordinates to place your quadrats at. This will help to make sure the results you get are representative of the whole sample area
2) count all the organisms you’re interested in within the quadrat
3) repeat steps 1 and 2 lots of times
4) work out the mean number of organisms per quadrat within the first sample area
5) repeat steps 1 to 4 in the second sample area
6) finally compare the two means
mean = total number of organisms/number of quadrats
calculations: estimating the population size
1) work out the mean number of organisms per m^2
2) multiply mean per m^2 by the total area (in m^2) of the habitat
environmental changes:
-the environment in which plants and animals live changes all the time. These changes are caused by abiotic (non-living) or biotic (living) factors and affect communities in different ways- for some species population size may increase, for others it may decrease, or the distribution of populations (where they live) may change
abiotic factors:
-light intensity: light is required for photosynthesis and the rate of photosynthesis affects the rate at which the plant grows. Also, plants can be food sources or shelter for many organisms
-temperature: temperature affects the rate of photosynthesis
-moisture levels: both plants and animals need water to survive
-soild 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 factors:
-food availability: more food means organisms can breed more successfully and therefore the population can increase in numbers
-new predators
-new pathogens: when a new pathogen arises the population has no resistance to it so they can be wiped out quickly
-competition: if one species is better adapted to the environment than another, then it will outcompete it until the numbers of the lesser adapted species are insufficient to breed
feeding relationships: 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 and food webs:
-food chains: show the feeding relationships between organisms, they are organised by trophic levels
-food webs: are a collection of different food chains to show how all the organisms in the habitat interact showing interpendence
pyramids of numbers:
-shows the population of each organism at each trophic level of the food chain
-producers are at the bottom and bars usually get smaller the further up you go
-however, if he producer is a large plant, e.g. tree, the size of he 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 of food chain
-it shows the relative dry mass of material at each level
-there is less biomass as you move up the trophic levels
-not all the food consumed by an animal is converted into biomass- this meand 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
energy transfer:
-producers (e.g. plants and algae) transfer about 1% of the incident energy from light for photosynthesis, as not all the ligh lands on the green (photosynthesising) parts of the plant
-only approximately 10% of the biomass of each trophic level is transferred to the next since:
-not all biomass can be eaten -> carnivores cannot generally eat bone, hooves, claws and teeth
-not all of the biomass eaten is converted into biomass of the animal eating it -> lots of glucose is used in respiration, which produces the waste product carbon dioxide + urea is a waste substance which is released in urin + biomass consumed can be lost as faeces-herbivores do not have all the enzymes to digest all the material they eat, so it is egested instead
efficiency of biomass transfer: (biomass transferred to the next level/biomass available at the previous level) x 100
-because less biomass is transferred each time it is common to have a limited number of trophic levels and to find less animals in the higher trophic levels
the carbon cycle:
-respiration: plants and animals aerobically respire, which releases CO2 into air + decomposers also respire while the break down compounds
-photosynthesis: plants remove CO2 from the air through photosynthesis
-decomposition: dead plants and animals are broken down by decomposers + the carbon is then returned into the atmosphere
-combustion: when plants and fossil fuels (remains of dead animals) are burnt, the carbon dioxide are released into the atmosphere
sulfur dioxide:
-released when fossil fuels are burnt
-dissolves in water droplets in clouds to form dilute sulfuric acid which creates acid rain
-acid rain makes rivers too acidic, which leads to aquatic organisms dying
-it corrodes metals and limestone in buildings
-it leeches minerals out of soil so plant and trees cannot survive
carbon monoxide:
-released when fossil fuels are burn through incomplete combustion
-binds irreversibly to haemoglobin, which then reduces the oxygen carrying capacity of red blood cells
-this can lead to tiredness, unscosciuos or even death in severe cases
-in pregnant women, insufficient oxygen affects the growth of the foetus
effects of global warming:
-climate change
-water levels will rise as glaciers melt from higher temperatures
-loss of habitats
-uninhabitable environments due to climate change means that some species will become extinct or they will migrate to more habitable areas
