Ecology And Our Impact On The Ecosystem

Question 1

What is a habitat?

Answer 1

The place where an organism lives

Question 2

What is a population?

Answer 2

A group of organisms of the same species living in a particular habitat

Question 3

What is a community ?

Answer 3

All the populations or organisms living and interacting with one another in a particular habitat

Question 4

What is an ecosystem?

Answer 4

A community together with its abiotic environment

Question 5

What is ecology?

Answer 5

The study of interactions of organisms with one another, as well as with their environment

Question 6

What is the abiotic environment?

Answer 6

Physical factors such as light intensity , water availability and soil pH

Question 7

What is the biotic environment?

Answer 7

Comprises of all the living things that an organism interacts with

Question 8

What are the physical features that make up the abiotic environment?

Answer 8

light intensity
Temperature
Amount of water available 
Oxygen content
Salinity of soil and/or water 
pH of soil and/or water

Question 9

How does light intensity affect the abiotic environment?

Answer 9

Light intensity affects the distribution and growth of plants and animals
Green plants exist only where there is adequate amount of sunlight
The growth of certain plants affect the distribution of animals in a location

Question 10

How does temperature affect the abiotic environment?

Answer 10

Temperature affects the physiological and metabolic activities of organisms by
affecting the rate of reaction of enzymes that control the physiological and metabolic activities of organisms
In winter-> enzymatic reactions proceed at a slower rate -> animals less active -> hibernate in the winter

Question 11

How does water affect the abiotic environment?

Answer 11

Organisms cannot live without water
- plants and animals that are found in environments whereby water is scarce is adapted for survival in those environments

Question 12

What are the factors that affects water availability?

Answer 12

Amount and pattern of rainfall

Air humidity

Question 13

How does oxygen affect the abiotic environment?

Answer 13

Oxygen is needed for aerobic respiration to occur

Question 14

What is salinity and how does it affect the abiotic environment?

Answer 14

Salinity is the salt concentration of water
High salt content in water can lead to
- water loss from cells of fish
- excess salt entering the cells of fish

Question 15

What are the problems faced by saltwater fish and how are they adapted for their environment?

Answer 15

Saltwater fish face
Water loss from cells and
Excess salt entering cells

Seawater is absorbed in their intestines
Kidney excretes salts and produces small amounts of concentrated urine

Question 16

What are the problems faced by freshwater fish and how are they adapted for their environment?

Answer 16

Salt loss from cells
Excess water entering cells

The cells in the gills uptake salts
Kidney reabsorbs salts and produce large amounts of diluted urine

Question 17

How does pH affect the abiotic environment?

Answer 17

Most organisms can only survive within a range of optimum pH
Eg acidophiles have been found to thrive in highly acidic conditions

Question 18

What are producers

Answer 18

Organisms that converts light energy from the sun into chemical energy in food eg green plants

Question 19

What are consumers

Answer 19

Organisms that obtain energy by feeding on other organisms

Question 20

What are decomposers?

Answer 20

Organisms that obtain energy by breaking down dead organisms, faeces and excretory products
Releases inorganic nutrients such as carbon and nitrogen for nutrient cycling
Eg fungi and bacteria

Question 21

What is a food chain?

Answer 21

A series of organisms through which energy is transferred, in the form of food
Usually doesn’t have more than 4 trophic levels
Illustrates feeding relationships between organisms

Question 22

Food chain sequence?

Answer 22

Producer-> primary consumers-> secondary consumers-> tertiary consumers

Question 23

What is a trophic level

Answer 23

A level or organism in a food chain

Question 24

Explain the non-cyclic energy flow in an ecosystem

Answer 24

The sun is the main energy source in an ecosystem
Light energy is converted into chemical energy by producers via photosysnthesis
Energy from producers are passed on from one trophic level to another via feeding
The flow of energy in an ecosystem is non-cyclic
Energy is lost to the environment as heat as it flows through the ecosystem

Question 25

How is energy lost from one trophic level to the next

Answer 25

Lost to the environment
As heat during respiration
In uneaten body parts or dead bodies
Through undigested matter egested by consumers (faeces)
Through waste products excreted by consumers (excretory products)
Approximately 90% of energy is lost when it is transferred from one trophic level to the next

Question 26

What is the usefulness of the pyramid of numbers?

Answer 26

Allows for the comparison of the number of organisms present in each trophic level at a particular time

Question 27

What is the usefulness of the pyramid of biomass?

Answer 27

Allows the comparison of the mass of organisms present in each trophic level at a particular time

Question 28

Why could a pyramid of numbers be inverted?

Answer 28

Organisms in one trophic level are parasitic on organisms of another , usually higher up trophic level
Many small organisms feed on a large organism

Question 29

Why could a pyramid of biomass be oddly shaped?

Answer 29

Organisms in one trophic level have a high reproductive rate

Question 30

What does a pyramid of energy represent

Answer 30

The total energy in each trophic level of a food chain over a certain period of time

Question 31

How does nutrient cycling occur

Answer 31

Through the physical, chemical and biological processes involving both the abiotic and biotic environments

Question 32

Why is the carbon cycle important?

Answer 32

To ensure a continuous supply of carbon dioxide for photosynthesis to take place
Enables energy to flow through the ecosystem via photosynthesis and feeding

Question 33

How is carbon cycled

Answer 33

Constantly removed and released into the atmosphere in the form of carbon dioxide

Question 34

How is carbon dioxide removed from the environment?

Answer 34

Through photosynthesis as green plants absorbs carbon dioxide from the atmosphere and use it to produce carbon compounds (eg glucose)
When animals feeds on plants the carbon compounds become part of their bodies
Fossil fuels- carbon compounds may be preserved as fossil fuels ( eg coal, natural gas)

Question 35

How is carbon dioxide released into the environment?

Answer 35

Respiration
- carbon compounds such as glucose are broken down into carbon dioxide

Combustion
- the combustion of fossil fuels such as coal and natural gas release carbon dioxide

Decomposition
- when organisms die the dead matter is broken down into simpler substances like carbon dioxide by decomposers

Question 36

What is a carbon sink

Answer 36

An area that stores carbon compounds for an indefinite period
It stores more carbon than it releases

Question 37

What are two examples of carbon sinks and how do they work

Answer 37

Oceans - largest carbon sinks on earth
Carbon dioxide that dissolves in the oceans water is absorbed and used by phytoplankton and algae in photosysnthesis
A portion of the carbon compounds found in oceans is buried in the seabed in the form of fossil fuel such as natural gas and oil

Forests
Atmospheric carbon dioxide is absorbed by the plants and used in photosynthesis
A large amount of carbon compounds is stored in trees in the forests
Remains of dead trees form coal, a fossil fuel

Question 38

What are the effects of deforestation?

Answer 38

Soil erosion
Forests provide a leafy canopy that protects the topsoil from direct impact of rain, helping retain water in the forest though the absorption of water by plant roots
In deforested areas soil is exposed to direct rainfall and the water is not absorbed or retained. Topsoil is easily washed away during heavy rain

Flooding
Rain -> soil erosion-> soil gets washed into river -> rise in water level -> increases chances of flooding

Desertification
No leafy canopy -> sunlight falls directly onto ground -> water evaporates from ground -> creates desert-like condition that is unsuitable for plant growth

Climate changes
Reduced plant life -> less carbon dioxide removed from atmosphere via photosynthesis-> more carbon dioxide in atmosphere -> enhanced greenhouse effect -> traps heat within the earth’s atmosphere -> warmer climates

Question 39

How do humans affect the ecosystem?

Answer 39

Humans use natural resources - depletion of natural resources will result in highly irreversible environmental damages
Human activities result in deforestation , overfishing and pollution

Question 40

What are the effects of overfishing/uncontrolled fishing practices?

Answer 40

Destruction of marine habitats

Decrease and extinction of certain fish populations

Question 41

What are some fishing techniques that are detrimental to the aquatic environment and how are they damaging

Answer 41

The use of dredges - destroys coral reefs and organisms that lives on the sea bed
The use of drift nets and trawlers - catches marine life indiscriminately, including young fishes, reducing their ability to mature and reproduce -> reduced population
Cyanide fishing - kills corals and other reef organisms

Question 42

What is pollution

Answer 42

The process whereby harmful substances (pollutants) are added into the environemnt

Question 43

What are the factors leading to water pollution?

Answer 43

Untreated sewage
Excessive usage of fertilisers and insecticides
Inorganic waste material

Question 44

What is sewage and how does it lead to pollution

Answer 44

Waste materials from homes and industries
Untreated sewage contains disease-causing bacteria that can cause epidemic if discarded into water bodies
-> eg cholera , epidemic disease caused by waterborne bacteria
Sewage and fertilisers contain phosphates and nitrates that can lead to eutrophication

Question 45

What are chemical fertilisers and how do they lead to pollution

Answer 45

Fertilisers containing nitrates and phosphates to increase crop yield
Excessive use can lead to eutrophication due to runoff into water

Question 46

What are the disadvantages of the pyramid of biomass?

Answer 46

Can vary during the year during the different seasons

Some organisms reproduce so quickly their biomass appears lesser than the next organism

Question 47

What are the causes and effects of eutrophication?

Answer 47

Untreated sewage and fertilisers that are not absorbed by crops may be washed by rainwater into nearby
rivers or lakes

The nitrates and phosphates in untreated sewage or fertilisers enhance the growth of algae and water plants. They are used in the synthesis of proteins and nucleic acids. This leads to the increased growth and multiplication of algae and floating water plants in the rivers or lakes this is known as eutrophication

Overgrowth of algae and floating water plants prevents sunlight from reaching the submerged plants.

Submerged algae and water plants die due to the lack of sunlight. The dead algae and water plants are decomposed by aerobic bacteria and fungi.

As the bacteria feed on the decaying organic matter , they grow and multiply rapidly , using up the oxygen in the water

Other organisms like fish die due to lack of oxygen

Question 48

What is inorganic waste and how does it lead to pollution?

Answer 48

Inorganic waste are poisonous metals like lead mercury zinc which are extremely harmful to humans

Waste water containing poisonous metals is discharged into water bodies
Poisonous metals are absorbed by the water plants present
The water plants are eaten by fish
Fish caught from the sea contains high concentrations of poisonous metals
Poisoning the villagers who eat the fish

Question 49

What is bioaccumulation

Answer 49

TB def: certain chemicals eg insecticides, DDT are not excreted but are accumulated in the bodies of organisms

When animals consume food containing non-biodegradable harmful substances like insecticides (eg: DDT) that cannot be excreted and instead is stored in the fatty tissues of animals that consume them. If consumers keep consuming food that contains DDT, the concentration will further increase in their bodies

Question 50

What is bioamplification?

Answer 50

TB def: certain chemicals that cannot be excreted but are accumulated in the bodies of organisms are then passed along the food chain increasing in concentration in the bodies of organisms along the trophic levels

The process whereby chemicals that cannot be excreted are passed along the food chain and become concentrated (accumulated) in the bodies of the final consumers

Question 51

What is conservation?

Answer 51

The protection and preservation of natural resources in the environment

Question 52

What is biodiversity?

Answer 52

The range of species that are present in a particular ecosystem

Question 53

Reasons for conservation \ why do we conserve the environment

Answer 53

To maintain biodiversity by preventing the extinction of species

• many wild plants and animals possess favourable genes thus by maintenance of a large gene pool , we can cross breed different varieties of wild plants and animals , thus improving agricultural produce
• plants are sources of medicinal drugs

For scientific research
- study of wildlife provides useful information to humans

For economic purposes

• tropical rainforests provide raw materials like rubber for industries
• also provides food eg rice was developed from rainforest plants

Food source
- marine life are a major source of human food

Maintenance of a stable and balanced ecosystem
-prevents the disruption of natural cycles like carbon cycles , prevents global warming

To preserve natural scenery and wildlife for people to appreciate
- natural resources enable outdoor recreational activities like hiking

Question 54

How do we conserve our forests?

Answer 54

Creation of laws to regulate the logging industry
Reforestation - the planting of new trees and\ or seedlings to replace trees that have been destroyed
Designation of lands as forest reserves
Research to improve on the quality of forests

Question 55

How can we conserve our fishing grounds ?

Answer 55

Banning the use of drift nets which indiscriminately trap all forms of marine life

Using nets with a certain mesh size so that young or immature fish are not caught

Regulating the entry of ships into fishing grounds

Limiting the period of fishing in fishing grounds

Banning the harvesting or fishing of endangered species; and raising endangered species of fish in hatcheries and releasing them into fishing grounds where the fish populations are decreasing

Question 56

What is an example of environmental biotechnology and how is it carried out

Answer 56

The use of decomposers in sewage treatment.

1. Wastewater is channeled into land reclamation plants through bar screens to remove large coarse material
2. Wastewater enters the primary settling tank and flows very slowly, allowing the solids suspensions to settle to the bottom of the tank and be removed and fed into an anaerobic digester as sludge.
3. The top liquids flows into an aeration tank and mixed with aerobic microorganisms, mainly bacteria with bubbles of compressed air pumped into the liquid. The dissolved oxygen is used by microorganisms for aerobic respiration when they absorb and breakdown organic pollutants in the water into harmless substances
4. The treated water and microorganisms are channeled to the final settling tank where the microorganisms settle to the bottom as sludge where a portion is reused in the aeration tank.
5. The excess is sent to the anaerobic digester and the clean water at the top of the tank is collected and discharged as affluent into nearby rivers streams or lakes
6. The anaerobic digester is a closed tank with no oxygen. Anaerobic bacteria decompose the sludge and produce biogas(mainly methane) that is used as fuel to generate electricity for the functioning of the reclamation plant
7. Remaining solid material is removed from the tank and may be used as fertiliser or incinerated