Investigating Ecosystems and Biodiversity

Unit 1 Summary – Living Environment

Investigating ecosystems and biodiversity

You need to know the following definitions:

Sampling Techniques

Sampling techniques can be used to sample the living and non-living parts of an ecosystem.

Factors related to living things such as food availability, number of predators, disease and competition are called biotic factors.

Non-living factors such as temperature, rainfall, light intensity and pH are called abiotic factors.

Remember this using………..

Factors affecting distribution of organisms

Abiotic factors affect the distribution of organisms. Here are some examples:

Daisies

• The more light available, the more daisy plants will be present.
• This is because daisies need light energy from the sun to make their own food by photosynthesis.

Grasses

• Grasses are found in the full sunlight of a field rather than in shady woodland.
• This is because grasses need lots of light energy from the sun to photosynthesise.

Adaptations

An adaptation is a feature of an organism that allows it to survive in its habitat.

Polar bears are well adapted for survival in the Arctic. Their adaptations include:

• white fur to camouflage from prey on the snow and ice
• thick layers of fat and fur for insulation against the cold
• a greasy coat that sheds water after swimming
• large furry feet to distribute their load and increase grip on the ice.

Camels are adapted to life in a hot climate. Camels live in deserts that are hot and dry during the day, but cold at night. Their adaptations include:

• large, flat feet to spread their weight on the sand.
• thick fur on the top of the body for shade, and thin fur elsewhere to allow easy heat loss.
• the ability to go for a long time without water - they don't store water in their humps, but they lose very little water through urination and perspiration.
• the ability to tolerate body temperatures up to 42ºC.
• slit-like nostrils and two rows of eyelashes to help keep out sand.

Identifying Organisms

A potential source of error that can occur while sampling is identifying organisms incorrectly. To overcome this source of error, a paired statement key or branching key can be used to identify organisms.

Branching Key

A key is a series of questions. Each question leads to another until eventually the name of the organism is found.

Paired statement key

Instead of asking questions at branching points on a diagram, you are asked to choose between two statements.

Each pair of statements is numbered and the instructions send you to the next relevant pair of statements.

Interdependence

You need to know the following definitions:

Photosynthesis

Photosynthesis is the process that plants use to make sugars using light energy. Light energy is trapped by chlorophyll which is found inside structures called chloroplasts. Plants use carbon dioxide from the air and water from the soils to produce the sugars (called glucose). They give off oxygen as a by-product of photosynthesis.

Respiration

Respiration is the process that releases chemical energy from food. All living organisms carry out respiration. Glucose and oxygen are used to make energy, water and carbon dioxide.

Nitrogen Cycle

Nitrogen is essential for the formation of amino acids in proteins. The nitrogen cycle explains how nitrogen is recycled. About 78% of the air is nitrogen. Because nitrogen is so unreactive, it cannot be used directly by plants to make protein. Only nitrates are useful to plants, so we are dependent on other processes to convert nitrogen in the atmosphereinto nitrates in the soil.

Nitrifying bacteria: Plants and animals can only use nitrates to make proteins as nitrogen gas is too unreactive. Nitrifying bacteria changenitrogen gas into nitrates which is a form of nitrogen that can be used by plants.

Denitrifying bacteria:Denitrifying bacteria change nitratesfrom the soil back into nitrogen gasin the atmosphere.

Root nodule bacteria: Nitrogen-fixing bacteria found in root nodules of leguminous plants (peas, beans and clover) fix nitrogen from the atmosphere into nitratesin the soil. Thisis a form of nitrogen that can be used by plants.

Free-fixing soil bacteria: Nitrogen-fixing bacteria found in the soil that fix nitrogen from the atmosphere into nitrates which is a form of nitrogen that can be used by plants.

The processes involved in the nitrogen cycle:

1. Nitrogen gas is converted to nitrates in the soil by nitrogen-fixing bacteria found freely in the soil calledfree-fixing bacteria or on root nodules of certain plants.Lightningalso converts nitrogen gas to nitrate compounds. Ammonia is converted to nitrates bynitrifying bacteriain the soil.
2. Plants absorb nitrates from the soil and use these to build upproteins. The plant may be eaten by animals, and the nitrogen is used to produceanimal protein.
3. Urea and waste material is broken down bydecomposers. This results in nitrogen being returned to the soil asammonia.
4. Decomposers also break down thebodiesof dead organisms resulting in nitrogen being returned to the soil as ammonia.
5. In some conditionsdenitrifying bacteriain the soil break down nitrates and return nitrogen to the air. This is usually inwaterlogged soil.

Fertilisers

Chemical fertilisers contain minerals such as nitrogen, potassium and phosphorus, which help plants to grow. Fertilisers increase crop production by replacing essential elements used by a previous crop or by boosting levels of such elements. Nitrogen particularly is needed to build plant proteins, thereby increasing growth.

Alternatives to chemical fertilisers include using manure and compost as a source of returning nutrients into soil. These alternatives do not harm the environment.

Eutrophication

A major problem with the use of chemical fertilisers occurs when they wash off the land by rainwater into rivers and lakes. The increase of nitrates and phosphates in the water allows a lot more algae to grow (an algal bloom). This prevents sunlight reaching other water plants, which then die. Bacteria break down the dead plants and use up the oxygen in the water so the other organisms in the lake cannot survive. eg. fish, snails, eels.

Diagram of Eutrophication

Carbon Cycle

The element carbon is the present in all living organisms. It is recycled through various processes, which are described in the carbon cycle.

Plants use carbon dioxide and sunlight to make their own food and grow. The carbon becomes part of the plant. Plants that die and are buried may turn into fossil fuels made of carbon like coal and oil over millions of years. When humans burn fossil fuels, most of the carbon quickly enters the atmosphere as carbon dioxide.

Importance of Nutrient Cycling

It is important that nutrients such as Nitrogen and Carbon are cycled so that they do not remain locked up in the bodies of dead animals and plants and are therefore available to other organisms.

Diagram of the Carbon Cycle

You need to know the following terms in the Carbon Cycle

Human influences on biodiversity

Human activities can have a large effect on the environment. Unfortunately many of our activities are harmful and decrease biodiversity.

Human activities that decrease biodiversity

Deforestation

Deforestation reduces biodiversity. Trees may be cut down to make wood products, to clear land for new buildings or roads, or for creating new farming or grazing land.

Deforestation can also occur as a result of natural disasters or accidental fires. When trees are removed or destroyed, the species living in theforest lose their natural habitats, and some are not able to survive the change.

Pollution

Pollution reduces biodiversity both on land and in the water. Any chemical in the wrong place or at the wrong concentration can be considered a pollutant.Transport, industry, construction and power generation all contribute pollutants to the air, land and water. Untreated sewage can also pollute water that people need for drinking and washing.

Chemicals found in fertilisers can also lead to eutrophication.

Burning fossil fuels

Climate change is caused by burning fossil fuels such as oil, coal and natural gas.The planet is getting hotter which means that some species cannot survive. The polar ice caps are melting which will cause sea levels to rise. This will mean that people will experience more floods. The climate is becoming more unpredictable and extreme events are becoming more frequent.eg. droughts, hurricanes, floods and storms.

Over exploitation

Over exploitation by humans causes massive destruction to natural ecosystems. People use wild species for food (fish), construction (trees), industrial products (animal blubber, skins), the pet trade (reptiles, fish, orchids), fashion (fur, ivory) and traditional medicines (rhino horn). This reduces biodiversity and may lead to extinction.

Human activities that increase biodiversity

In order to reduce the negative impact that humans have had on biodiversity, a number of different conservation methods have been developed.

Seed and Gene banks

Seeds and DNA are collected from wild species and kept in special temperature controlled rooms so that they can be sued in the future if the species becomes extinct.

National Parks and Marine Protected Areas

Hunting and collecting wild species is not allowed in National Parks or Marine Protected Areas, so wild species are able to survive and reproduce. This increases biodiversity in the area.

Captive Breeding Programs

Captive breeding programs are designed to breed organisms that are either threatened or extinct in the wild. These organisms may then be released to boost the wild population and keep the species alive. eg. pandas in Edinburgh Zoo.

Extinction

Extinction is when the last member of a species has died out. The most famous example of an extinct species is the Dodo which was a flightless bird.

Species that are under threat of extinction in the wild include:

Indicator Species

Indicator species - a species whose presence or absenceindicates the level of pollution in the environment.

Indicator species can provide an early warning of environmental changes. They can be used to assess the health of an environment or ecosystem – they are often termed bio-indicators.

Non-native (invasive) species