Ecosystem

Question 1

What is ecology ?

Answer 1

Ecology is the study of interrelationships between organisms and those between organisms and the physical environment

Question 2

What is species ?

Answer 2

Species is basic unit of classification that the same species can interbreed to form a fertile offspring

Question 3

What is population ?

Answer 3

Population is a group of organisms of same species living in a same habitat

Question 4

What is community ?

Answer 4

Community refers to all populations of different species living in a same habitat

Question 5

What is ecosystem

Answer 5

Ecosystem is the natural unit of living components and non-living components

Question 6

What is biome ?

Answer 6

Biome is a complex of communities that occupy a large geographical area, and characterized by a dominant type of plant

Question 7

What is biosphere?

Answer 7

Biosphere refers to the entire space on the earth’s surface where organisms exist

Question 8

What makes the ecosystem self-supporting, stable and yet dynamic

Answer 8

In an ecosystem, the interactions of organisms with one another and with the physical environment lead to the flow of energy and cycling of materials. These factors cause the ecosystem self-supporting, stable and yet dynamic

Question 9

What are the major types of ecosystem in HK ?

Answer 9

woodland, fresh water steam, mangrove, rock shore and glass land

Question 10

What is the abiotic factors in ecosystem ?

Answer 10

Abiotic factors are the non-living components of a ecosystem of an ecosystem. Examples included, temperature, light intensity, day length, rainfall and humidity, wind speed, water current, salinity, oxygen concentration of oxygen and soil properties

Question 11

What are habitat and niche of an organism ?

Answer 11

• habitat is the place that organism lives
• niche of an organism is the role played by the organism in its community. It is determined by the temperature range in which the organisms lives, the type of food they eat and the space it occupies

Question 12

What are species diversity and dominant species in a community ?

Answer 12

• species diversity refers to the variety of organisms that make up of a community. It determined by the species richness and abundance of different species in the community
• dominant species are the species in the community that exert strong control over the composition and diversity of the community. In terrestrial ecosystem, they usually the commoners types of plants

Question 13

What is predation ?

Answer 13

• Predation is the interaction between two species in which one hunts, captures and kills other for food
• the organisms eating other is the predator
• the organisms being eaten is called prey
• the amount of predator is always lagging behind that of prey

Question 14

What is competition ?

Answer 14

•competition means fighting for the same needs, eg. Food, shelter, mates and sunlight
•intraspecific competition:
~competition between the organisms of same species
~more intense because individuals of the same species have same needs
•interspecific competition
~competition between the organisms of different species

Question 15

Name three types of symbiotic relationships

Answer 15

• commensalism
• mutualism
• parasitism

Question 16

What is commensalism ?

Answer 16

• two organisms live together in such way that one gain benefit while the other is not affected
• eg. Barnacles live on the body of whales

Question 17

What is mutualism ?

Answer 17

• two organisms may live together in such way that both gain benefits.
• lichens growing on a piece of rock

Question 18

What is parasitism ?

Answer 18

• two organisms live on or inside other organisms, obtain benefits from them and cause harm
• the organisms gain benefits is called parasite
• the organisms being harmed is called host
• eg. Tapeworm lives inside the intestine of mammals and obtain nutrients

Question 19

What is ecological succession ?

Answer 19

• Ecological session is the serious of change in the composition of a community over a period of time
• the variety of species in a community in an ecosystem changes gradually as a result of interactions between organisms and the physical environment

Question 20

What is the involved in the ecological succession ?

Answer 20

• in the process of ecological succession, organisms modify their environment in ways that allow other species to come in and replace them.
• the species diversity progressively increases as more and more species appear in the community
• the species diversity reaches the maximum when a climax community is reached. The climax community consists the maximum number of organism that can be supported by a habitat
• it is stable unless there are sudden changes in environment eg.fire, drought

Question 21

What is primary succession ?

Answer 21

•primary succession starts with the colonization of a barren area where there is no soil and organisms before

Question 22

What is the process involved in the primary succession ?

Answer 22

• When lava cools down, it forms barren rocks. Lichens are often the first types of species to colonize a barren area because they are able to grow in adverse, dry conditions. Lichen spores are brought to the barren rocks by wind. As the lichens grow they form the pioneer community Organic matter accumulates and the rocks are broken up into smaller particles, forming soil.
• Mosses, ferns and grass start to grow. They become established over most part of the rocks and become the dominant species. They provide food and shelter for plant-eating animals Dead, decaying plants and animals, as well as animal waste form humus which further enriches the soil. The soil becomes thick enough for the growth of shrubs. The shrubs grow over the grass and ferns and become the dominant species. animals are attracted to the habitat because there are more food and shelter.
• Finally, the soil becomes thick and rich in nutrients. It can support the growth of trees which grow over the shrubs, and the trees become the dominant species. The habitat becomes a woodland that attracts increasing numbers of animals (e.g, birds). A climax community is reached.

Question 23

What is the process involved in the secondary succession ?

Answer 23

•The stages that take place in secondary succession are similar to succession except the following:
~the pioneer community of lichens is not needed as soil is already present;
~secondary succession usually develops more quickly than primary succession. This is because seeds, roots and underground vegetative organs of plants may still survive in the soil. They grow and develop into new plants rapidly once conditions become favourable.

Question 24

What are the differences between primary succession and secondary succession.?

Answer 24

• Primary succession takes place in barren areas where no soil or organisms were present before. It takes a longer time to reach a climax community
• Secondary succession takes place in areas where organisms were once present but is now barren. It takes a shorter time to reach a climax community.

Question 25

Explain the difference between the energy stored in biomass and the energy gained at each trophic level.

Answer 25

* The amount of energy stored in biomass is always less than the amount of gained at each trophic level * because energy is lost as heat during respiration / only part of the energy gained is used for growth /energy is lost in form of metabolic wastes

Question 26

Suggest two reasons to explain why in each trophic energy that can be provided previous trophic

Answer 26

* Energy is lost/ trapped in the undigested/ unabsorbed parts of organisms of the previous level * Energy is lost in the uneaten parts of organisms of the previous level * Energy trapped in the dead bodies of organism is not available to the organisms of next higher trophic level /is redirected to the decomposers