Topic 7: Ecology

Adaptations, Interdependence and Competition

Communities (7.1.1) An individual is part of a species but lives in its habitat within a population. Organisms are adapted to live in the conditions of their environment. Community = 2+ populations of organisms interacting in the same habitat. Populations are often dependent on each other. Ecosystem = the interaction of a community (biotic) with non-living (abiotic) parts of the environment. Also is 2+ populations of organisms in their environment. Species = a group of organisms that can interbreed to produce fertile offspring.    -   For example, a horse and a donkey can interbreed with one another but their offspring (a mule) will be unable to reproduce        as mules are infertile. The fact that offspring cannot reproduce shows that horses and donkeys belong to two different        species. Habitat =  Population = all the organisms of the same/closely-related species in an area. Abiotic = non-living The animals rely on the plants for food, and the plants rely on the animals to distribute their seeds. Competition between organisms which need the same resources: competition either within a species / between different species plants may compete for light, space, water and mineral ions in the soil animals may compete for territory (space), food, water and mating partners Interdependence = how organisms in a community depend on other organisms for vital services (e.g. food) including food, shelter and reproduction (pollination, seed dispersal); e.g. birds take shelter in trees, flowers are pollinated by the help of bees the removal/addition of a species to a community can affect the population greatly → changes prey/predator numbers stable community = all biotic and abiotic factors are in balance thus the population sizes remain roughly the same (consistent) when they are lost it's difficult to replace them  e.g. tropical rainforests, oak woodlands, coral reefs e.g. simple food chain: grass → rabbit → fox; if the foxes were killed, rabbit population would increase as they are no longer prey to foxes. As a result amount of grass would decrease since the increased population of rabbits would be eating it.

Abiotic Factors (7.1.2) = non-living factors. Abiotic factors that can affect a community: Light intensity (animals + plants) required for photosynthesis rate of photosynthesis affects the rate at which the plant grows plants can be food sources or shelter for many organisms Temperature (animals + plants) affects the rate of photosynthesis both animals and plants have evolved to grow healthily at their optimum temperatures Availability of water/Moisture levels plants and animals need water to survive many plants cannot survive in waterlogged soils - their roots are unable to respire. Other plants (e.g. pitcher plants) grow best in bogs where the moisture levels are high. Soil 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) many plants require high levels of soil mineral to grow well. Carnivorous plants (e.g. pitcher plants) have evolved to catch insects to supplement the low levels of mineral in their soil different species of plants thrive in different nutrient concentration levels some plants (azaleas) grow best in acidic soil, some (clematis) prefer alkaline, some (hydrangea) can grow in both the flower colour of plants like hydrangea changes in different soils Wind intensity and direction has a huge impact on where organisms are found within an ecosystem - many organisms prefer 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 affects the rate of transpiration (movement of water from root to leaves) in plants transpiration affects the temperature of the plant and the rate of photosynthesis because it transports water and mineral ions to the leaves Carbon dioxide (plants) affects the rate of photosynthesis in plants - CO₂ is a reactant in photosynthesis also affects the distribution of organisms as some thrive in high CO₂ environments  woodlands often have higher CO₂ levels than open grassland, so many plants living in open areas have evolved mechanisms to overcome a shortage of CO₂ areas with higher levels of CO₂ are more likely to have healthy plants growing farmers often release CO₂ within their greenhouses to maximise crop yield  Oxygen levels (aquatic animals) levels in water vary greatly, unlike in the air most fish need a high concentration of oxygen to survive healthy lakes and rivers have high levels of oxygen, whereas polluted waters have low levels, meaning only certain species can survive (e.g. sludgeworms)

Biotic Factors (7.1.3) = living factor Biotic factors that can affect a community: Food availability  more food = organisms can breed more successfully and therefore the population can increase in numbers New predators New pathogens when a new pathogen (microorganism that can cause a disease) 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

Adaptations (7.1.4) Organisms have adaptations that allow them to survive in the conditions where they live. Structural: shape/colour of a part of an organism  sharp teeth of a carnivore to tear meat apart camouflage, like the tan/brown colour of a lionnesses coat, to avoid prey from spotting it species in cold environments may have a thick layer of fat for insulation Behavioural: the way an organism behaves individuals may play dead to avoid predators basking in the sun to absorb heat courting behaviour to attract a mate Functional: involved in processes such as reproduction and metabolism late implantation of embryos conservation of water through producing little sweat   Extremophiles live in environments which have extreme conditions. These include high temperatures, pressures or salt concentrations.     e.g. bacteria which live in deep sea vents where the pressure is very high.   Adaptations for different scenarios -    cold climates: smaller surface area to volume ratio to reduce heat loss, lots of insulation (blubber, fur coat) -    dry climates: adaptations to kidneys so they can retain lots of water producing very concentrated urine, being active in the      early morning and evenings when it is cooler, resting in shady areas, larger surface area ratio to increase heat loss -    examples of plant adaptations: curled leaves to reduce water loss, extensive root systems to take in as much water as possible,       waxy cuticle to stop water evaporating, water storing tissue in stem -   cactus adaptations: shallow roots, spines to prevent them being eaten, can store water in their leaves -   snow fox adaptations: white fur to blend in, small ears to reduce heat loss, thick coat

Organisation of an Ecosystem

Levels of Organisation (7.2.1) Feeding relationships are shown by a food chain starts with a producer always photosynthetic organisms (usually a green plant/algae) they make glucose through photosynthesis (sun provides their energy) used to make other biological molecules in the plant, which make up the biomass ​​​​​​​​​​​​​​producers are eaten by primary consumers - energy is transferred through organisms in an ecosystem when one is eaten by another primary consumers are eaten by secondary consumers  secondary consumers are eaten by tertiary consumers prey = animals eaten predator = consumers that eat and kill prey A stable community will show population cycles between the predators and prey If the population of prey increases, the population of predators will also increase. This will result in the number of prey decreasing after some time as more would be consumed by the increased number of predators. When there isn’t enough prey to feed all the predators, the population of predators will decrease, which will allow the population of prey to increase again. → = eaten by