Ecology and the environment Flashcards
habitat
the place where an organism lives
population
all the organisms of one species in a habitat
community
all the different species in a habitat
ecosystem
all the organisms living in a particular area and all the non living (abiotic) conditions (eg: temperature, climate, soil type)
what is biodiversity
it is the variety of different species of organisms on Earth, or within an ecosystem
why is high biodiversity important
it makes sure that ecosystems are stable because different species depend on each other for things like shelter and food. different species can also help to maintain the right physical environment for each other (eg: the acidity of the soil)
what is reducing biodiversity
lots of human actions including deforestation, pollution and global warming
environmental changes affecting communities in different ways:
- the environment in which plants and animals live changes all the time. these different changes are caused by abiotic (non living) and 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 may change
abiotic factors affecting communities:
- environmental conditions. other environmental conditions that affect the abundance and distribution of organisms include light intensity (plants only) , moisture level and soil pH
- toxic chemicals. eg. chemical pesticides or fertilisers. pesticides can build up in foods 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 eutrophication, which leads to the death of organisms
biotic factors affecting communities:
- availability of food: in s bumper year of berries, the population of blackbirds might increase because there would be enough food for all of them, so they are more likely to survive and reproduce
- number of predators: if the number of lions (predator) decreases then the number of gazelles (prey) might increase because fewer of them will be eaten by lions
competition - organisms compete with other species (and members of their own species) for the same resources. Eg. plants need things like light, space, and water and minerals from the soil. Animals compete for things like space (territory), shelter, food, water, and mates.
what is a quadrat
it is a square frame enclosing a known area. To compare the population size of an organism in two sample areas
using a quadrat to study the population size of small organisms
- place a 1m 2 quadrat on ground at random point within the first sample area. You can do this by dividing the sample area into a grid and using a random number generator 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
- count all the organisms you’re interested in within the quadrat.
- repeat steps 1 and 2 many times
- work out the mean number of organisms per quadrat within the first sample area
- repeat steps 1 and 4 in the second sample area
- compare the two means
using belt transects to study distribution across a habitat
- mark out a line in the area you want to study
- then collect data along the line using quadrats placed next to each other. count all the organisms of the species you’re interested in
- record the other data , such as the mean height of the plants you are counting or the abiotic factors in each quadrat. (eg use a light meter to measure the light intensity)
- repeat steps 1-3 several times, then find your mean number of organisms or mean percentage cover for each quadrat
- plot graphs to see if the changing abiotic factor is correlated with a change in the distribution of the species you’re studying
food chains show what is eaten by what in an ecosystem:
- food chains always start with a producer eg a plant. producers make (produce) their own food using energy from the sun
- producers are eaten by primary consumers, primary consumers are then eaten by secondary consumers and secondary consumers are eaten by tertiary consumers.
- all these organisms eventually die and get eaten by decomposers. eg bacteria. decomposers break down (decompose) dead material and waste.
- each stage (eg producers, primary consumers) is called a trophic level
food webs show how food chains are linked:
- there are many different species within an environment - which means lots of different possible food chains. you can draw a food web to show them.
- all the species in a food web are interdependent, which means id one species changes, it affects all the others.
pyramids of numbers
- each bar of numbers shows the number of organisms at that stage of the food chain.
- every time you go up a trophic level, the number of organisms, go down. This is because it takes a lot of food from the level below to keep one animal alive.
pyramids of biomass
- each bar on a pyramid of biomass shows the mass of living material at that stage of the food chain - (basically how much all the organisms at each level would ‘weigh’ if you put them all together.
pyramids of energy transfer are…
always pyramid shaped
pyramids of energy transfer:
- pyramids of energy show the energy transferred to each trophic level in a food chain. eg when a rabbit eats a dandelion is gets energy, which the dandelion got from the sun.
- pyramids of energy transfer are always the right shape - regular pyramid
energy is transferred along a …
food chain
energy is transferred along a food chain:
- energy from the sun is the source of energy for nearly all life on earth
- plants use energy from the sun to make food during photosynthesis. this energy then works its way through the food chain as animals eat the plants and each other.
- not all the energy that is available to the organisms in a trophic level is passed on to the next trophic level - around 90% of the energy is lost in various ways
-some parts of food eg roots or bones, are not eaten by organisms so the energy is not taken in. some parts of the food are indigestible (eg fibre) so pass through organisms and comes out as waste (eg faeces) - a lot of energy that does get taken in is used for staying alive (ie in respiration which powers all life processes)
- most of this energy is eventually transferred to the surroundings by heat
- only around 10% of the energy available becomes biomass, (ie it is stored or used for growth)
- this is the energy that is transferred from one trophic level to the next.
materials are constantly recycled in an eco system
- materials that organisms need to survive, such as carbon and nitrogen are recycled through both biotic and abiotic components of the ecosystems
- this means they pass through both living organisms (the biotic components of an ecosystem) and things like the air, rocks. and soil (abiotic components of an ecosystem) in a continuous cycle
the carbon cycle shows how…
carbon is recycled
state –> carbon is an important element in the materials that living things are made from. but there is only a fixed amount of carbon in the world. this means that is is constantly recycled
carbon cycle diagram
- there is only one arrow going down from CO2 in the air. the whole thing is powered by photosynthesis. green plants use the carbon from CO2 to make carbohydrates, lipids and proteins
- eating passes the carbon compounds in the plant along to animals in a food chain or web
- respiration by living plants and animals releases CO2 back into the air.
- plants and animals eventually die and decompose or are killed and turned into useful products
- when plants and animals decompose they are broke down by micro organisms, such as bacteria and fungi. these micro organisms are known as decomposers and they release enzymes, which catalyse the breakdown of dead material into smaller molecules. decomposers release CO2 back into the air by respiration as they break down the material
- some useful plant and animal products eg wood and fossil fuels, are burned (combustion) This also releases CO2 back into the air.
- decomposition of materials means that habitats can be maintained for the organisms that live there. eg nutrients are returned to the soil and waste material (such as dead leaves) doesn’t just pile up.
nitrogen fixation
the process of turning N2 from the air into nitrogen compounds in the soil which plants can use.
nitrogen is recycled in the nitrogen cycle:
- the atmosphere contains about 78% nitrogen gas, N2. This is a very unreactive and so it cannot be used directly by plants or animals
- nitrogen is needed for making proteins for growth, so living organisms have to get it somehow.
- ## plants get their nitrogen from the soil, so nitrogen in the air has to be turned into nitrogen compounds (such as nitrates) before plants can use it. Animals can only get proteins by eating plants or eachother
carbon monoxide is poisonous
- when fossil fuels are burnt without enough air supply, they produce the gas carbon monoxide (CO)
- it is a poisonous gas. if it combines with haemoglobin in red blood cells, it prevents them from carrying oxygen
- carbon monoxide’s mostly released in car emissions. most modern cars are fitted with catalytic converters that turn the carbon monoxide into carbon dioxide , decreasing the amount of CO that is released into the atmosphere
2 main ways nitrogen fixation happens
- lightning: there is so much energy in a bolt of lightning that it is enough to make nitrogen react with oxygen in the air to give nitrates
- nitrogen fixing bacteria in soil and the roots of some plants
4 types of bacteria involved in the nitrogen cycle
- decomposers : break down proteins (in rotting plants and animals) and turn them into ammonia. This forms ammonium ions in the soil
- nitrifying bacteria: turn ammonium ions in decaying matter into nitrates (nitrification)
- nitrogen fixing bacteria: turn atmospheric N2 into nitrogen compounds that plants can use
- denitrifying bacteria: turn nitrates back into N2 gas. This is no benefit to living organisms
some of these bacteria live in the soi and some of them live in nodules on plant roots.
acid rain is caused by sulfur dioxide
- burning fossil fuels releases harmful gases like CO2 and sulfur dioxide(SO2)
- the sulfur dioxide comes from sulfur impurities in the fossil fuels
- when this gas mixes with rain clouds it forms dilute sulfuric acid
- this then falls as acid rain
- internal combustion engines in cars and power stations are the main causes of acid rain
green house gases trap energy from the …
sun
acid rains kills fish and trees:
- acid rain can cause a lake to become more acidic. this can have a severe effect on the lake’s ecosystem. many organisms are sensitive to changes in pH and cannot survive in more acidic conditions. many animals and plants die
- acid rain can kill trees. the acid damages leaves and released toxic substances from the soil, making it hard for the trees to make up nutrients
acid rains kills…
fish and trees
greenhouse gases trap energy from the sun:
- the temperature of the earth is a balance between the energy it gets from the sun and the energy it radiates back out into space
- gases in the atmosphere absorb most of the heat that would normally be radiated out into space, and re radiate it in all directions (including back towards the earth) THIS IS CALLED THE GREENHOUSE EFFECT
- if this did not happen, then at night there would be nothing to keep any energy in, and we would quickly get very cold
- there are several different gases in the atmosphere that help keep the energy in. they are called ‘greenhouse gases’ and they include water vapour, carbon dioxide, and methane.
global warming - the earth is heating up
- human beings are increasing the amount of carbon dioxide in the atmosphere. we are also increasing the levels of other gases that can act as greenhouse gases. eg CFS and nitrous oxide . This has enhanced the greenhouse effect
- a result of this is the earth heating up
- climate change could lead to things like extreme weather and rising sea levels and flooding due to the polar ice caps melting. this could cause habitat loss, and could affect food webs and crop growth
state –> human activity produces lots of greenhouse gases
the types of greenhouse gases huma activity produces:
carbon dioxide
methane
nitrous oxide
CFC’s
carbon dioxide
- humans release carbon dioxide into the atmosphere all the time as part of our everyday lives - in car exhausts, industrial processes, as we burn fossil fuels etc
- people around the world are also cutting down large areas of forest (deforestation) for timber and to clear land for farming - and this activity affects the level of carbon dioxide in the atmosphere
methane
- methane gas is produced naturally from various sources. eg rotting plants in marshland
- however, two ‘man made’ sources of methane are on the increase.
nitrous oxide
- nitrous oxide is released naturally by bacteria in soils and the ocean
- a lot more is released from soils after fertiliser is used.
- it is also released from vehicle engines and industry
CFC’s
- CFC’s are man made chemicals that were once used in aerosol sprays (eg deodorant) and fridges. They’re really powerful greenhouse gases.
- most countries have agreed not to produce them anymore because they also damage the ozone layer that prevents UV radiation from reaching earth.
- but some CFC’s still remain and get released, eg by leaks from old fridges
fertilisers can leach into …
water and cause eutrophication
eutrophication
- nitrates and phosphates are put onto corn fields as mineral fertilisers
- if too much fertiliser is applied
