Unit 7 - Biology: Ecology Flashcards Preview

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Flashcards in Unit 7 - Biology: Ecology Deck (13):
1

What is the principal source of energy input to biological systems

The Sun

2

Define the terms:
Decomposer
Ecosystem
Trophic level

Decomposer: an organism that gets its energy from dead or waste organic matter

Ecosystem: a unit containing all of the organisms and their environment, interacting together, in a given area eg decomposing log or a lake.

Trophic level: the position of an organism in a food chain or food web

3

Define the terms:
Food chain
Food web
Producer
Consumer
Herbivore
Carnivore

Food chain: a chart showing the flow of energy (food) from one organism to the next, beginning with a producer (eg mahogany tree -> caterpillar -> song bird -> hawk)

Food web: a network of interconnected food chains showing the energy flow through a part of an ecosystem

Producer: an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis

Consumer: an organism that gets its energy by feeding on other organisms

Herbivore: an animal that gets its energy by eating plants

Carnivore: an animal that gets its energy by eating other animals.

4

Describe energy losses between trophic levels

The available energy decreases along a food chain.
The energy that is lost includes loss through respiration and feces, as well as the organic material that is not consumed by organisms in the next trophic level.

At every step in a food chain, energy is transferred as heat to the surroundings. The amount of energy arriving in a useful form at the end of a chain is only a small fraction of the amount of energy at the beginning.

For example
Grass transforms the sun's energy into stored chemical energy. Only a small proportion of this energy gets into a rabbit because energy is wasted. Some of the grass is eaten and digested by the rabbits, absorbed into their bodies and used in their cells - but a lot of the grass they eat is not digested. (it passes out the body as feces).
The rabbits will not eat all of the grass. Some will be trampled, old, tough and inedible. Nowhere near all the stored chemical energy in the grass will be passed onto rabbits.
More energy is wasted when the chemical energy in grass is transferred into other forms of energy inside the rabbits' bodies. A lot will be transferred into heat energy, which is given out from the rabbit to the air around it.

5

Explain why food chains usually have fewer than five trophic levels

Food chains are generally only 5 organisms long because the number of organisms decrease along a food chain because the available energy decreases. The longer the food chain, the more energy is lost. There would not be enough energy left to support a population of fifth consumers at the end.

6

Describe the carbon cycle

The level of CO2 in the atmosphere is maintained by several processes including PHOTOSYNTHESIS, RESPIRATION and COMBUSTION.

-green plants remove CO2 from the atmosphere by photosynthesis
-living organisms (including all plants and animals) (bacteria/decomposers respire) release energy from their food using respiration
-respiration and combustion (burning) both release CO2 into the atmosphere.
-fossil fuels combusting

These processes form a carbon cycle in which the proportion of carbon dioxide in the atmosphere remains about the same.

7

Discuss the effects of the combustion of fossil fuels and the cutting down of forests on the oxygen and carbon dioxide concentrations in the atmosphere

When land is cleared to timber and farms, there are fewer trees to remove CO2 from the atmosphere by photosynthesis. If the fallen trees are burnt or left to rot, additional CO2 is released into the atmosphere. This is particularly important when forests are cleared to make way for farms. Not only are there then fewer trees to absorb CO2, but the burning of the trees release more CO2

*if the trees are left to rot = food for fungi and bacteria = more CO2 from respiration

8

List the undesirable effects of deforestation

Extinction
Loss of soil
Flooding
Carbon dioxide build up

Soil erosion: When rains falls on a hillside covered with grass and trees it will cause little if any erosion. The vegetation absorbs the impact of the rain on the soil. The rain soaks gently into the soil. Much of it is absorbed by the plants. But on a bare hillside the force of the rain drops landing on the soil splashes soil particles up into the air. They fall back to earth lower down the hillside. The soil particles gradually move down the hill.

Biodiversity loss: trees, shrub and other plants provide shelter, food and shade for an enormous range of bacteria, fungi, insects, animals and birds. When deforestation occurs, it generally is harder for the environment to sustain this variety, simply because not all organisms can survive in the same habitat or conditions.

Local climate change: lack of shade, massive increase in desert terrain as soil deprived of constant moisture eventually can turn into largely barren sand

Agricultural and financial losses: with less rain, crops typically cannot get enough water to thrive and produce a good field, and food shortages happen.

Global warming: less photosynthesis and more CO2 produced when plants burn = harder for heat to escape out into space potentially contributing to the greenhouse effect and increasing global warming.

Cultural displacement.

9

Describe the undesirable effects of pollution

-Water pollution by sewage and chemical waste
-air pollution by greenhouse gases (carbon dioxide and methane) contributing to global warming'

Water pollution is caused by the discharge of harmful substances into rivers, lakes and seas. Many aquatic invertebrate animals cannot survive in polluted water, so their presence or absence indicates the extent to which a body of water is polluted.

Pollutant | Typical effect
fertilisers | damage to aquatic ecosystems
sewage | kills aquatic organisms and harms human health
toxic chemicals | kill aquatic organisms and harm human health

Air pollution
-Global warming (When sunlight reaches the earth it passes through our atmosphere. Greenhouse gases such as CO2 are invisible to sunlight, also known as shortwave radiation because of its short wavelength. THis allows the sunlight to pass through the atmosphere unhindered by greenhouse gases, and warm the Earth's surface.
The warm surface of the Earth radiates infrared heat, also known as longwave radiation because of its long wavelength. Greenhouse gases absorb longwave radiation. This results in the atmosphere trapping some of the Earth's heat as it tries to escape out to space.. Heat trapping gases such as CO2 make the atmosphere warmer than it would be without any greenhouse gases.
We are adding CO2 by burning fossil fuels. As more greenhouse gases accumulate in the atmosphere, more heat is being trapped. This causes global warming)
-The effects of pollutants
Some of these pollutants are directly harmful to humans. For example, carbon monoxide is toxic and, if breathed in, can cause death.
Others pollutants are harmful to the environment, so cause harm to humans indirectly. For example, sulfur dioxide causes acid rain that can damage or kill trees and crops

10

Describe the undesirable effects of overuse of fertilisers (include eutrophication of lakes and rivers)

Farmers use fertilisers to help their crops to grow better and get higher yields. Many famers use inorganic fertilisers. They often contain 3 minerals that are especially important to plants - nitrates, phosphates and potassium. They are called the NPK fertilisers. Other farmers use organic fertilisers, such as waste from farm animals.

Whichever kind of fertiliser is used, it is important that the farmer makes sure that the fertiliser gets used by the crop it is intended for, and does not get wasted. If it is wasted the farmer wastes money and the fertiliser may pollute streams, rivers and lakes. This happens because if the crop does not take up the fertiliser quite quickly, and it rains, then he rain may leach the fertiliser from the soil and into a water course.

When NO3- and phosphate ions enter a water course they can be used by algae and water plants. Often the algae starts to grow really fast - algal bloom - where the water goes thick and greener where its surface is covered by a thick blanket if green algae. Some of these algae produce toxins which can kill animals that drink the water.

The algae also blocks the sunlight from reaching other aquatic plants which some of the organisms in that habitat rely on.

WHen the algae dies its bodies provide food for bacteria - bacteria population increases. The bacteria respire and use up oxygen, so the amount of oxygen in the water decreases. There may not be enough oxygen for animals such as fish, so the fish either swims away to a different unpolluted part of the water course or they die..

11

Discuss the causes and effects on the environment of acid rain, and the measures that might be taken to reduce its incidence

Acid rain is any form of precipitation like rain, fog, snow or hail that contains harmful substances such as nitrogen and sulphur acids.

Whenever we burn fossil fuels we release waste gases such as carbon dioxide, sulphur dioxide and various oxides of nitrogen. The main sources of these are cars and power stations.
Sulphur oxide and the oxides of nitrogen will mix with rainwater in clouds and form acidic solutions. These then fall as acid rain.

-Acid rain weaken trees by damaging their leaves, limiting the nutrients available to them, or exposing them to toxic substances slowly released from the soil. Acidic water dissolves the nutrients and helpful minerals in the soil and then washes them away before trees and other plants can use them to grow.
-Damages buildings made from limestone because the rainwater slowly dissolves minerals in the rocks. It has a corrosive effect on limestone or marble.
-The water will also make rivers and lakes more acidic. As acid rain flows through soils in a watershed, aluminium is released from soils into the lakes and streams located in that watershed. As pH in a lake or stream decreases, aluminium levels increase. Both low pH and increased aluminium are directly toxic to fish. Low pH and increased aluminium levels cause chronic stress that may not kill individual fish, but leads to lower body weight and smaller sizes and makes fish less able to compete for food.
-The increased acidity of the water also allows aluminium salts to dissolve more easily. The aluminium ions are very poisonous to fish and birds.

Possible solutions:
-use coal that contain less sulphur
-the powerplant can instal equipment called scrubbers, which remove the sulphur dioxide from gases leaving the smoke stack by electrostatic
-cleaner cars
-wash sulphur out of the coal before it's burned

The solution is to basically produce less greenhouse gases.

To do this we well need to use less fossil fuel. This includes our use of materials and power that rely on them.

In addition to this we can reduce the amount released from source, that is to remove the gases before they are released.

To do this, we can build power stations that have acid gas "scrubbers" to remove them from the chimneys. We can also use catalytic converters in our car exhausts which break up the greenhouse gases as they leave our cars

12

Explain how increases in greenhouse gases (carbon dioxide and methane) are thought to cause global warming

When sunlight reaches the earth it passes through our atmosphere. Greenhouse gases such as CO2 are invisible to sunlight, also known as shortwave radiation because of its short wavelength. THis allows the sunlight to pass through the atmosphere unhindered by greenhouse gases, and warm the Earth's surface.
The warm surface of the Earth radiates infrared heat, also known as longwave radiation because of its long wavelength. Greenhouse gases absorb longwave radiation. This results in the atmosphere trapping some of the Earth's heat as it tries to escape out to space.. Heat trapping gases such as CO2 make the atmosphere warmer than it would be without any greenhouse gases.
We are adding CO2 by burning fossil fuels. As more greenhouse gases accumulate in the atmosphere, more heat is being trapped. This causes global warming.

13

Describe the need for conservation of
-species and their habitats
-natural resources (limited to water and non-renewable materials including fossil fuels)

For centuries man has been using and abusing the resources in his environment. The consequence for living organisms and their habitats has been species extinction, habitat destruction, loss of diversity.
The consequence for our natural resources is reduction and fragmentation of habitats and landscapes, loss of species of flora and fauna.

Conservation is important to make sure certain changes don't happen too quickly. Rapid change can force animals, plants, places or people to become endangered or extinct.

We need to conserve to make certain we have resources for ourselves and for people in the future. Many natural resources are necessary for our survival, which is why we cannot run out of these resources.

If we don't conserve species, food chains and webs will also become dismantled, resulting in a negative consequence for many other different species.