TPS Science Department Biology 4.7 Ecology

Transcription

1 TPS Science Department Biology 4.7 Ecology R Ashbee 2017

2 Communities An ecosystem is a community of interacting organisms (living things) and their physical environment. For example, a river ecosystem consists of the river, the riverbed, the plants growing in the river, microorganisms living in the river and animals living in the river. Within an ecosystem there are different levels of organization: Individual: A single organism (e.g. a tuna fish) Population: A group of individuals of a given species that live in a particular area at one time. For example, all the tuna fish living in this section of the sea currently. Community: All the populations of different species living in a certain area and time. For example, the populations of tuna fish, salmon, jellyfish, crabs and seaweed living in this part of the sea at this time. Ecosystem: The community plus the non-living surroundings e.g. rocks and water. We call the community the biotic part of the ecosystem, and the nonliving surrounding e.g. rocks and water, the abiotic part. R Ashbee

3 Questions: 1. Define organism. 2. Define ecosystem. 3. Describe the four levels of organization in an ecosystem, and give examples. 4. Define biotic 5. Define abiotic R Ashbee

4 Competition and Interdependence Competition Individual organisms are in competition with other individuals, both from the same and from other species. For example, a fern competes with other ferns and plants of different species for light. Plants often compete for: light, space, mineral ions and water. Animals often compete for: food, mates and territory. Materials To survive and reproduce, organisms require a supply of materials from their surroundings and from the other living organisms there. For example, a fern needs light from the Sun, and water and nutrients from the ground. The nutrients are made available from decaying organisms, detritivores and microorganisms in the soil. Interdependence Within a community each species depends on other species for food, shelter, pollination, seed dispersal etc. This is called interdependence. If one species is removed it can affect the whole community. A stable community is one where all the species and environmental factors are in balance so that population sizes remain fairly constant. R Ashbee

5 Questions 1. What factors do plants compete for? 2. What factors do animals compete for? 3. What is interdependence? 4. What would happen to the number of rabbits in a forest ecosystem if the foxes were struck by a disease? R Ashbee

6 Abiotic and biotic factors Abiotic factors are the non-living parts of an ecosystem that can affect the community: Light intensity Temperature Moisture levels Soil ph and mineral content Wind intensity and direction Carbon dioxide levels (for plants) Oxygen levels (for aquatic animals) Biotic factors are the living factors in an ecosystem which can affect a community: Availability of food Predators Pathogens (diseases) Availability of mates R Ashbee

7 Questions 1. Copy and complete: R Ashbee

8 Adaptations Organisms have features that enable them to survive in the conditions in which they normally live. These features are called adaptations. Adaptations may be structural, behavioural or functional. Structural adaptations: These are physical features of an organism such as: deep roots for obtaining water in dry habitats; large feet to prevent sinking in soft surfaces such as snow or sand; hollow bones to allow flight. Functional adaptations: These are features of how a process occurs in the organism, for example photosynthesis in plants; reabsorption of water from urine and faeces in desert-dwelling animals. Behavioural adaptations: These are actions that the organism takes in order to survive, such as migration, resting in the heat of the day or huddling with other individuals to conserve body heat and moisture. Extremophiles Some organisms live in environments that are very extreme, such as at high temperature, pressure, or salt concentration. These organisms are called extremophiles. An example is the bacteria living in deep sea vents. R Ashbee

9 Questions: 1. What is an adaptation? 2. Define structural adaptation and give two examples. 3. Define functional adaptation and give two examples. 4. Define behavioral adaptation and give two examples. 5. Define extremophiles and give an example. R Ashbee

10 Levels of organisation Feeding relationships within a community can be represented by food chains. All food chains begin with a producer which synthesizes molecules. Producers are usually green plants or algae which make glucose using photosynthesis. Producers are eaten by primary consumers. These may be eaten by secondary consumers which may be eaten by tertiary consumers. Consumers that kill and eat other animals are called predators, and those that are eaten in this way are called prey. R Ashbee

11 In a stable community, the numbers of predators and prey rise and fall in cycles. Questions 1. What is a producer? 2. What do we call an organism that eats a producer? 3. What do we call an organism that eats a primary consumer? 4. What do we call an organism that eats a secondary consumer? 5. What do we call an organism that kills and eats animals? 6. What do we call animals that are killed and eaten? 7. Copy and label the food chain. 8. Copy the graph showing predator and prey numbers over time and explain its shape. R Ashbee

12 Measuring distribution and abundance The abundance of a species is the number of individuals in a given area. For example, the abundance of Bengal tigers in the India Sundarbans area is approximately 70. The distribution of a species the geographical area inhabited by the population. For example, the distribution of the Cicindela beetle is limited to cool mountain environments. Ecologists use a range of methods to determine the distribution and abundance of species in an ecosystem. It is usually not possible to count an entire population. Instead, ecologists use sampling methods and then scale up to reach an estimate. Below are described the two main sampling methods: The quadrat method: A quadrat is usually a square made of wire. It may contain further wires to mark off smaller areas inside, such as 5 x 5 or 10 x 10 squares. The organisms underneath, usually plants, can be identified and counted. When using a quadrat, it should be placed randomly so that a representative sample is taken. The validity and reproducibility of the results increases as the results from more quadrats are analysed. Quadrats may also be used for slow-moving animals such as slug and snails. R Ashbee

13 The transect method: A transect is a line across a habitat or part of a habitat. It can be as simple as a string or rope placed in a line on the ground. The number of organisms of each species can be observed and recorded at regular intervals along the transect. Questions 1. Explain what distribution is and give an example. 2. Explain what abundance is and give an example. 3. Why do ecologists use sampling techniques? 4. Describe how a quadrat can be used to estimate the population in an area. 5. Describe how the transect method can be used to observe variations in abundance across a space. R Ashbee

14 The water cycle The water cycle provides fresh (not salty) water for plants and animals on land before draining into the sea. Water is continuously evaporated and precipitated (falls as rain and snow). Questions 1. Copy the diagram of the water cycle. 2. Starting with water in the sea, describe how water moves around the water cycle. 3. What is fresh water? 4. What is evaporation? 5. What is precipitation? 6. Why is the water cycle important for life on earth? R Ashbee

15 The carbon cycle All living organisms contain carbon. Molecules such as cellulose and glucose contain carbon. This carbon is returned to the atmosphere through respiration and is then used by plants in photosynthesis. Plants make molecules such as cellulose and glucose and the cycle is complete. Microorganisms play an important part in decaying dead animals and plants. Microorganisms perform respiration using the carbon in dead organisms and release carbon dioxide into the atmosphere as part of the carbon cycle. In addition, they return mineral ions to the soil. Questions 1. Copy the diagram of the carbon cycle 2. Describe what happens in the carbon cycle 3. Name three groups of organisms that preform respiration 4. Which organisms take carbon out of the atmosphere and create glucose with it? 5. In what way do plants depend on the carbon cycle? 6. In what way do animals depend on the carbon cycle? 7. In what way do microorganisms depend on the carbon cycle? R Ashbee

16 Biodiversity Biodiversity is the variety of all the different species of organisms on Earth, or within and ecosystem. A high biodiversity ensures the stability of ecosystems by reducing the dependence of one species on another for food, shelter, or the maintenance of the physical environment. The future of the human species on Earth depends on us maintaining a good level of biodiversity. Many human activities are reducing biodiversity. Questions 1. Define biodiversity. 2. Name three things that species depend on other species for. 3. Why is high biodiversity important? R Ashbee

17 Waste management Rapid growth in the human population and an increase in the standard of living mean that increasingly more resources are being used and more waste is being produced. Unless waste and chemical materials are properly handled, more pollution will be produced. Pollution can occur: in water from sewage, fertilizer or toxic chemicals in air from smoke and gases on land from landfill and toxic chemicals Pollution kills plants and animals. This can reduce biodiversity. Questions 1. Give two reasons why more waste is being produced now compared to 100 years ago. 2. Why is it important to deal properly with waste? 3. Describe three areas that pollution can occur in and give examples for each. 4. State two effects of pollution. R Ashbee

18 Land use Humans reduce the amount of land available for other animals and plants by doing the following things: building quarrying farming dumping waste Peat Peat is a material similar to soil made of partially decayed plants. Areas where the ground is made of peat are important habitats. Many of these areas have a lot of water as well as peat and are called peat bogs. Peat is collected from peatlands and bogs to use for cheap compost for food production. Peat is also burned as a fuel. The destruction of peat bogs, and other areas of peat (peatlands) to produce garden compost, reduces the area of this habitat and reduces the biodiversity. The decay and burning of peat releases carbon dioxide into the atmosphere, contributing to global warming. R Ashbee

19 Questions 1. State four ways humans reduce the land available for plants and animals 2. What effect will reducing habitats have on biodiversity? 3. What is peat? 4. State two uses of peat. 5. What is the disadvantage of using peat for compost? 6. What is the disadvantage of burning peat for fuel? R Ashbee

20 Deforestation Humans have caused large-scale deforestation (destruction of forests) in tropical areas in order to: provide land for rice fields and cattle grow crops for biofuels However this has reduced habitat and biodiversity. Questions: 1. What is deforestation? 2. Give three reasons for deforestation 3. Explain why deforestation is a problem R Ashbee

21 Consequences of global warming Carbon dioxide and methane are both greenhouse gases, and their levels in the atmosphere are increasing. The scientific consensus is that this is contributing to global warming. Some biological consequences of global warming are: Destruction of habitat due to flooding caused by rising sea levels Change in habitat due to changing weather e.g. droughts in some areas Some reptiles and fish are sensitive to temperature when sex of offspring is being determined so an imbalance in the sexes may arise The scientific consensus on global warming Global warming is a complex phenomenon with a great many variables. It is very far removed from the experiments we do in school where we change one variable and measure the effect on another. This means that it is impossible to draw certain conclusions from single studies. For this reason, in order to draw conclusions about global warming and the role of humans in it, scientists look at large numbers of studies by other R Ashbee

22 scientists and compare their results. The consensus is the agreement reached by most scientists. The scientific consensus is that human activity is contributing to global warming. Questions 1. Name two gases that contribute to global warming 2. Describe three biological consequences of global warming 3. What is another term (an appositive) for the agreement of most scientists? 4. What does the scientific consensus on global warming say? 5. Why is evidence uncertain around the role of humans in global warming? R Ashbee

23 Maintaining Biodiversity Like all other organisms, humans interact with their ecosystems. Often, human activity has had a negative effect on the biodiversity of the ecosystem. These activities include: The destruction of habitats for agriculture, power production or building Pollution of water systems from manufacturing, landfill and sewage Hunting of animals Scientists, governments and concerned citizens have put in place programmes to reduce the negative effects of human on ecosystems and biodiversity: Breeding programmes for endangered species Protection and regeneration of rare habitats Reintroduction of field margins and hedgerows in agricultural areas Reduction of deforestation and carbon dioxide emissions Recycling resources rather than dumping waste in landfill Questions 1. Define ecosystem. 2. Define biodiversity. 3. Describe three ways humans can have a negative effect on the biodiversity of an ecosystem. 4. Describe five ways humans try to reduce their negative effects on ecosystems. 5. Create sentences from the following stems: R Ashbee

24 a) Humans often have a negative effect on an ecosystem because b) Humans often have a negative effect on an ecosystem, but c) Humans often have a negative effect on an ecosystem, so R Ashbee