B16 Adaptations, interdependence and competition Flashcards
What is a community?
is two or more
populations of organisms.
What is an ecosystem
is the interaction between a
community
of living organisms and their environment. It is also two or more populations of organisms (usually many more) in their environment.
What is a population?
A population is all the organisms of the same or closely-related
species in an area.
What is interdependence and give an example?
All organisms in an ecosystem depend upon each other. If the population of one organism rises or falls, then this can affect the rest of the ecosystem.
A simple food chain is:
grass → rabbit → fox
If the foxes in the
food chain above were killed, the population of rabbits would increase because they are no longer prey to the foxes. As a result the amount of grass would decrease because the increased population of rabbits would be eating it.
Often very small changes to ecosystems have large consequences, which can be difficult to predict. This means that all the organisms in an ecosystem are dependent upon each other. We call this
interdependence.
What is a stable community?
A stable community is one in which the size of the populations of all species remain relatively constant over time. In the example above the amount of grass, and the numbers of rabbits and foxes all remain relatively constant. The different populations are living in a healthy balance with their environment.
What are abiotic factors?
Non-living elements of an ecosystem, such as climate, temperature, water, and soil type.
What are examples of abiotic factors?
Light intensity
Some plants have evolved for
optimum
growth in bright sunlight. An example of this is a cactus houseplant. Cacti originally come from deserts where they grow in bright sunlight. Other plants have evolved to grow in shade.
Many orchids, which are also kept as houseplants, grow on trees in the rainforest and have evolved for optimum growth in darker conditions. If you were to put an orchid on a bright windowsill and a cactus in a dark corner of your room neither plant would grow well.
Temperature
Both animals and plants have evolved to grow healthily at their optimum temperatures. If you planted either your cactus or orchid houseplants outside in cold temperatures, they would die. Similarly, animals that have evolved to live at the North Pole, such as the polar bear, could not survive in warmer conditions.
Moisture levels
More people kill houseplants by overwatering than by under-watering them. Many plants cannot survive in waterlogged soils. Their roots are unable to
respire
, they rot and the plant dies. Other plants, such as pitcher plants, grow best in bogs where the moisture levels are high. Soil moisture meters can accurately determine how wet an area is.
Soil pH content
The pH of soils can have a huge effect on the plants that are able to grow in them. Some plants, like azaleas, grow best in acidic soils and will quickly die if planted in alkaline soils. Others, like clematis, prefer alkaline soils. Some, like the hydrangea, can grow in both. These plants are unusual in that their flower colour changes in different soils. Just like universal indicator paper, hydrangea flowers are pink in acidic soils and blue in alkaline soils.
Soil mineral content
Many plants require high levels of soil minerals to grow well. An example of this is magnesium, which is required to produce chlorophyll. Plants with unnaturally yellow leaves may have a magnesium
deficiency
. Carnivorous plants, such as pitcher plants, have evolved to catch insects to supplement the low levels of minerals found in the soils in which they grow.
Wind intensity and direction
The strength of the wind and its direction has a huge impact on where organisms are found within ecosystems. Many organisms prefer more sheltered locations. Plant seeds are more likely to settle and germinate there, and animals which depend upon these are more likely to live close to where they grow. The strength of the wind can also affect the growth of individual organisms.
Carbon dioxide levels for plants
Carbon dioxide is a reactant in
photosynthesis
which means plants need it to survive. Areas with higher levels of carbon dioxide are more likely to have healthy plants growing. Farmers often release carbon dioxide within their greenhouses to maximise their
crop yield
. Woodlands often have higher carbon dioxide levels than open grassland, so many plants living in open areas have evolved mechanisms to overcome a shortage of carbon dioxide.
Oxygen levels for aquatic animals
Oxygen from the air and oxygen produced by aquatic plants dissolves in water. Without this, aquatic animals would suffocate and die. Healthy lakes and rivers have high levels of oxygen, and polluted waters often have low levels of oxygen. This pollution means that only certain
species can survive there such as sludgeworms. These are bioindicator species because their presence or absence informs us about the condition of the habitat.
What are biotic factors?
Living elements of an ecosystem, such as plants and animals.
Give examples of biotic factors
Availability of food
All animals require food to live. The availability of food is a major factor in how many animals live in an
ecosystem
. Areas like rainforests with rich food supplies have more
species
of life than other areas like deserts and the Polar Regions where there is less food.
New predators
A tree suffering from Ash dieback disease
Figure caption,
Ash dieback disease
The arrival of new
predators in an ecosystem can have a devastating effect. In balanced ecosystems, predators and
prey have evolved together. Predators can catch enough prey to survive, but not so many that they kill all of their food.The arrival of a new predator can upset this balance. An example of this is the introduction of the red fox to Australia, which has caused concern over their effect on native birds and small mammals. Introducing new predators can cause a rapid decline in the numbers of prey, which then reduces the food supply for existing predators.
New pathogens
When organisms inhabit new ecosystems they often bring new
pathogens
. As an example, Europeans first colonised North America, and introduced new pathogens, like the influenza virus. Many Native Americans had not developed immunity to new diseases such as this, and so many were killed by them. There are many examples of new pathogens being introduced to the UK. Ash dieback is a disease caused by a fungus which has killed many ash trees since it was first found in the UK in 2012.
Pathogens have also been introduced on purpose. Myxomatosis is a disease that affects rabbits. It is caused by a virus and infected rabbits develop skin tumours and may go blind. In the 1950s it was purposefully released into the wild in the UK to reduce the
population
of rabbits. It did exactly this and some people estimate that more than 99 per cent of rabbits in the UK died. However, our rabbits developed immunity to it and the population has now returned to previous levels.
Out-competition
The introduction of a new species into an ecosystem can result in it out-competing another native species. Several hundred years ago grey squirrels were brought over from North America by wealthy people and let free in their grounds. Our smaller native red squirrel couldn’t compete with the newer, larger grey squirrel. Because grey squirrels are larger they can store more fat and survive harsher winters. So the numbers of red squirrels and the places they live has reduced dramatically.
Other examples of out-competition of native species by newly introduced species include the Canada goose in Europe and the cane toad in Australia, Himalayan balsam in Cambodia and harlequin ladybirds are also current concerns.
What do plants compete over?
Light
All plants and algae need light to
photosynthesise
. Plants compete for light by growing quickly to reach it and often shade other plants with their leaves. When an old tree in a forest dies and falls to the ground, there is a race to fill in the gap in the canopy. It doesn’t look like a race to us because it happens slowly.
Water from the soil
Water is a reactant in photosynthesis and it is essential that plants have a regular supply of water for the process to occur. Some fully grown trees, like the oak tree, lose a staggering 150 litres of water per day, which is used to transport materials through the plant to the leaves. Some plants have roots that are shallow but extend a long way from the tree to maximise the update of water after rainfall. Others have roots that are deep to find stores of underground water.
Minerals from the soil.Plants require minerals for healthy growth. These include nitrates and magnesium. Without sufficient minerals plants suffer
deficiency diseases because they cannot grow healthily. Plants that grow in soils with few minerals, such as bogs, have evolved different ways of accessing nitrates. Some, like the Venus flytrap and pitcher plants, have evolved to be carnivorous and consume insects, enabling them to grow more successfully than their competitors on mineral poor soil.
Space
Plants also require space for healthy growth. This means their leaves are not shaded which maximises photosynthesis. Some gardeners have experimented by planting vegetables very close together. These result in much smaller vegetables being produced.
Competition can be
intraspecific, for example competition between oak trees in a forest, or
interspecific such as when another
species of tree like birch or yew grew next to oak trees. When a woodland tree dies, other younger trees compete to replace it. This competition ensures the growth of the healthiest individuals, and maintains vigour in the population.
Individuals within a species that cannot compete effectively are unlikely to reproduce, and may die. This is known as survival of the fittest and is a driver for evolution. Whole species that are unable to effectively compete may become
extinct.
What is the difference between interspecific and intraspecific competition.
Intraspecific competition means The competition between organisms within the same species.
while
Interspecific competition means
The competition which occurs between organisms of different species for a common resource.
What do animals compete over?
Food
All animals require food which provides them with energy and raw materials to complete life processes, without which they may die. Because of these, competition for food can be fierce. There are many birds which eat insects in our gardens, and some have evolved to only eat certain types of insect to reduce competition from other
species. Others like the blue tit and great tit compete with other members of their own species and as well as others for different insects. Because food is so vital, many animals will fight for it.
Mates
Animals within a species also compete for mates. This is essential so they can pass on their genes to their offspring. Animals have evolved to have an innate or natural drive to reproduce, and this competition often results in fights. This is seen each year when animals like red deer group together at the start of the mating season. Large male deer fight with each other by locking antlers and pushing hard, which is called a rut. In deer, and many others species, these fights competing for mates can often result in serious injury or death, but benefits the population as only the strongest pass on their genes to the next generation.
Territory
The territories of animals contain all of the resources and conditions they need to survive. These include
abiotic factors such as light, temperature and water, and oxygen for aquatic animals. There are also
biotic factors such as food and predators. Many animals, including the cats in back gardens, will fight for territory.
An example of
intraspecific competition over territory would be between lions on the grass plains of Africa whereas
interspecific
competition would occur when another
predator like leopards lived close to the lions.
So overall they compete for food mates and territory.
How to use a quadrat?
Choose a starting point on the school field in an area where the grass is often cut
Use
random
numbers to generate a set of coordinates to place your first
quadrat.
Count the number of different plant
species within this quadrat (the species richness).
Return to your starting position and repeat steps two and three a further 14 times using different random numbers.
Repeat steps one to four for a part of the school field in which the grass is infrequently cut.
Compare your results by calculating a
mean for each location.
What is quantitative sample?
records the number than the type
What does a Quadrat sample?
Number of an individual species - the total number of individuals of one species (eg daisies) is recorded.
Species richness - the number of different plant or animal species is recorded but not the number of individuals within a species.
Percentage cover - the percentage of the quadrat area that is covered by one species (eg grass). This is easier to estimate if a quadrat has wires making smaller sections. Percentage cover rather than number of individuals is used when estimating plant frequencies if it is difficult to identify individual plants, such as grasses or moss.
