Ecology Flashcards
Ecology meaning
is the study of the various interactions between living things (organisms) and their environment.
An ecosystem refers to
organisms and their interactions with their environment.
The biosphere is
the part of the planet inhabited by organisms.
A habitat is
where an organism lives
Environment
All external factors that influence living things are referred to as its environment.
Environmental factors affecting organisms:
Abiotic factors are non-living factors (these include edaphic factors which relate to the soil) that aftect organisms.
Biotic factors are living factors which affect organisms.
Climatic factors refer to weather conditions over a long period of time that affect organisms.
Abiotic factors
non-living factors (these include edaphic factors
Biotic factors
Biotic factors are living factors which affect organisms.
Climatic factors
Climatic factors refer to weather conditions over a long period of time that affect organisms.
Aspect effect on organisms
The direction an ecosystem faces. In the northern hemisphere, southern-facing slopes get more sun.
Eg. Sun-seeking plants tend to grow on south-facing slopes.
Exposure
The extent to which organisms are vulnerable to the environment eg. exposure to wind
Eg Strong winds can disrupt plant root contacts in the soil
Steepness
Steep slopes lose water quickly & soils are washed away.
Eg
Conifers can grow on steep slopes as leaves retain water.
Altitude
Height above sea level.
Higher altitudes are cooler and have decreased oxygen availability.
Eg
Some plants eg. mosses and animals eg. birds are adapted to living at high altitudes.
Currents
Plants and animals can be washed away to various locations.
Eg seaweed attached to rocks
Edaphic: clay soil
Small particles leaving little room for air and water to pass through
Eg few plants and animals thrive here due to lack of available oxygen and water and the difficulty penetrating the soil
Sandy soil
Large particles leaving lots of room for oxygen and water.
However, since water passes through easily, nutrients are.
quickly washed out.
Eg plants with long roots grow well in sandy soil as it is easily penetrable
Organic matter (humus)
Humus provides nutrients, binds soil particles and helps retain water and minerals.
Eg
Provides food to earthworms.
Plants grow here due to the abundance of nutrients.
Soil ph
The degree of acidity or alkalinity of the soil.
Different plants are adapted to different soil pH eg.
heather grows in acidic soils, lavender grows in alkaline soils. Most plants grow best
in neutral (pH = 7) soil.
Air content
Provides oxygen for organisms.
Eg
Oxygen is required for aerobic respiration of plants and animals. Lack of oxygen stunts growth and can lead to death.
Mineral content
Can influence soil pH. Plants require certain minerals for survival eg. magnesium for photosynthesis.
Eg high water content can lead to minerals being washed out of the soil which can effect soil ph. If there are insuffficient minerals present plants cannot grow
Water content
Water in the soil is absorbed by plant roots
Eg
Plants need water for
photosynthesis and for general transport of nutrients and minerals.
Biotic: humans
Human activity can both positively and negatively impact ecosystems.
Eg
Pollution harms the ecosystem. Conservation parks can improve and maintain biodiversity.
Pollination and seed dispersal
Plants often depend on other organisms to reproduce
Eg
Flowers attract insects with bright colours the pollen sticks to the insect, and when the insect flies away it disperses the pollen to other flowers. Animals can disperse seeds by eating the plants and excreting its seeds.
Competition
A struggle for a limited resource eg. territory, water
Example
Plants compete with each other for light, animals compete with each other for food.
Parasitism
Parasites weaken their hosts and may reduce their numbers.
Eg
Fleas infect foxes & rats.
Predation
Certain species survive by killing and eating other species.
Eg
The rabbit population may be controlled by the fox population killing and eating them for survival.
Food
The availability of food determines how many organisms can survive.
Eg
If there is an abundance of plants available, many herbivores will survive. If there is an abundance of herbivores, predators will survive by eating them.
Climatic: light intensity
Light is required for photosynthesis
Eg
Trees grow tall to get more light. Plants grow in the areas that receive the most light.
Day length
Affects plant flowering & germination, as well as migration & hibernation in animals
Eg
Most plants in the northern hemisphere grow better during the spring and summer when the days are longer as there is more sunlight and hence more energy for photosynthesis.
Temperature
Influences growth rates of organisms, hibernation and migration patterns.
Eg
Bears hibernate in the winter to avoid the cold season.
Wind strength
Can cause physical damage to plants eg. effects root attachment to the soil.
Increases evaporation.
Eg
Trees grow better on the sheltered side of the slope
Salinity
Controls the movement of water by osmosis
Eg
If the external environment is high in salt, water will move out of the organism into the environment (principle behind salting food to kill bacteria)
Humidity
Amount of water Vapor in the air
Influences the evaporation of in the air
from the soil and from plant stomata. If there is high humidity, water cannot evaporate.
Rainfall
Water is essential for metabolism, transport and photosynthesis.
If there is too much rainfall soils can become waterlogged and drained of nutrients, which will inhibit plant growth and hence animal survival. If there is not enough rainfall, plants will be unable to survive.
Factors affecting aquatic ecosystems:
Waves can cause damage to organisms, which influences how animals adapt e.g. barnacles have tough outer shells.
Currents can transport warm and cold water to a habitat, which can impact certain organisms’ abilities to survive there.
Light can only penetrate the upper layers of bodies of water. As plants need light for photosynthesis, most aquatic plants are found in the upper layers of water. Since organisms feed off plants, they are also usually found in the upper layers.
The salinity of the water influences the movement of water in and out of organisms.
Freshwater amoeba have a contractile vacuole for osmoregulation
Energy flow
The sun is the main source of energy for the planet, and energy flows in one direction. Sun -
Producers > Consumers.
• Producers are organisms that carry out photosynthesis. This includes all plants (autotrophic).
Consumers are organisms that take in food from another organism. This includes all animals. Primary consumers feed on producers, secondary consumers feed on primary consumers, tertiary consumers feed on secondary consumers.
Tropic level
is a feeding stage in the food chain. Only 10% of the energy is passed onto the next trophic level, with the remaining 90% being used by the organism or lost as heat.
Grazing food chain
is a sequence of organisms in which each organism is eaten by the next member of the sequence (only one species at each trophic level).
A food web
contains two or more interlinked food chains (may be many species at one trophic level).
A pyramid of numbers
is a visual representation of the number of organisms at each trophic level in a food chain. A pyramid of numbers can be useful for comparing the number of organisms at each trophic level of different food chains.
Constructing a pyramid of numbers
•Consider the food chain: leaves -> beetle -> spider - blackbird
• The producer (leaves) will make up the base of the pyramid. There will be thousands of leaves, so this level is the biggest.
The primary consumer (beetles) will make up the next level of the pyramid.
The secondary consumer (spiders) will make up the next level of the pyramid.
The tertiary consumer (blackbird) will be the top level of the pyramid.
Remember that only 10% of energy is passed on between trophic levels. For this reason, the number of organisms will decrease as you go up with pyramid (if it is a normal pyramid.
Limitations of use
• The pyramid of numbers does not account for the size of the organism at each level, which can result in several different shapes of pyramid eg. an inverted pyramid.
• Consider the food chain: oak tree - squirrel + fox + flea
• Think of how many squirrels can live on a single oak tree. Even though the oak tree is huge, its numbers are small. The producer (the oak tree) makes up the base of this pyramid but it will be represented by a single line.
• The next level of the pyramid is the primary consumer, the squirrel. This level will be much bigger than the first level, since many squirrels can live on a single oak tree.
• The next level of the pyramid is the secondary consumer, the fox. There must be more squirrels than foxes, otherwise the foxes wouldn’t survive, so this level is smaller than the second level.
• The final level of the pyramid represents fleas, a parasite. Think of how many fleas can live on a single fox. Therefore this level is going to be the biggest.
• Hence not every pyramid of numbers looks like a typical pyramid.
An ecological niche
is the role of an organism in its ecosystem.
Nutrient recycling
Nutrient recycling is the re-use of nutrients.
The Carbon Cycle:
• The carbon cycle refers to the way in which organisms take in and give out carbon to and from the environment.
Plants take in carbon dioxide when they carry out photosynthesis.
Plants give out carbon dioxide when they carry out respiration.
• Animals take in carbon from the environment when they eat plants.
Animals give out carbon dioxide when they carry out respiration.
When animals die, they are acted on by decomposers such as bacteria and fungi, which releases carbon dioxide into the environment.
Fossil fuels are made from decomposing plants and animals. When we burn fossil fuels eg.
coal, we are releasing carbon dioxide into the environment.
Nitrogen cycle
The Nitrogen Cycle:
•The function of the nitrogen cycle is to take nitrogen from the environment and make it available for organisms to use.
•Nitrogen gas in the air is converted to ammonia (NHs) and other nitrogenous compounds such as ammonium (NH*) or nitrate (NO;) by a process called nitrogen fixation. It is an anaerobic process that is mainly carried out by nitrogen-fixing bacteria in the soil or roots of plants such as legumes.
Nitrogen fixation can also occur as a result of lightning strikes, volcano eruptions and industrial processes (eg. the Haber process)
Nitrates are taken in (assimilated) by plants (and animals when they eat plants). The nitrates are converted into plant & animal amino acids which form proteins, and nucleic acids which form RNA and DNA
When plants or animals die, decomposition of the dead organisms is carried out by bacteria & fungi of decay, found in the soil. They release nitrogenous compounds such as ammonia (NHs) into the soil.
• Nitrification is the conversion of ammonia and ammonium (NH*) compounds into nitrite and then into nitrate. This is carried out by chemosynthetic, nitrifying bacteria in the soil.
Some of these nitrates are assimilated by plants from the soil, while some nitrates are acted upon by denitrifying bacteria.
Denitrification is the conversion of nitrates into nitrogen gas. This is an anaerobic process.
Human impact
Three ways in which humans affect environments are pollution, conservation and waste management
Pollution
Pollution is the addition of harmful substances to the environment.
Types include
domestic pollution (household waste),
agricultural pollution (insecticides, slurry)
and industrial pollution (chemical waste).
Pollutant
A pollutant is any harmful addition to the environment.
