Community and Ecosystem

Question 1

Define species

Answer 1

A group of similar organisms which can interbreed to produce offsprings

Question 2

Define population

Answer 2

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

Question 3

Define community

Answer 3

Population of different species living in the same habitat

Question 4

Define ecosystem

Answer 4

A few communities which lives together and interact with one another

Question 5

Give 2 examples of plants which prefers acidic soil

Answer 5

• pineapple

- rose

Question 6

What are the 3 types of topography

Answer 6

• altitude
• gradient
• aspect

Question 7

Explain chemoautotropic organisms

Answer 7

• organisms which can produce their own food in the absence of light
• gain energy through the oxidation of inorganic substances
• eg: nitrobacter, rhizobium sp.

Question 8

In the food chain, how is energy lost?

Answer 8

90% energy lost via radiation during

• respiration
• excretion
• any living processes

Question 9

Arrange in ascending order the trophic levels according to the number of each organisms

Answer 9

tertiary consumer –> secondary –> primary –> producers

Question 10

What is the interaction in a lichen & sea anemone and hermit crab. explain the interaction

Answer 10

• Mutualism
• Lichen consists of algae and fungi. Fungi supplies water minerals and protection whereas algae undergoes photosynthesis to provide nutriets for itslef and the fungi.
• Sea anemone obtains a free ride and nutrients from the leftover food. Hermit crab obtains protection as sea anemones have poisonous stings

Question 11

What are the difference between intraspecific competition and interspecific competition

Answer 11

• -Inter–
• competition between members of different species
• stronger species survive while weaker species extinct
• -Intra–
• competition between members of same species.
• strong members remain while weak members extinct

Question 12

Give 2 abiotic components of the mangrove ecosystem

Answer 12

• exposed to strong wind and waves
• high light intensity
• muddy soil which lacks aeration
• high salt concentration and low oxygen content in water

Question 13

Explain 2 adaptations for mangrove plants

Answer 13

• sunken stomata // thick succulent leaves: reduce R.O.T due to exposure to high light intensity
• hydathodes : excrete excess salts
• lenticels: to allow gaseous exchange
• old leaves store excess salt before falling off
• viviparous seedlings: germinate while still attached to parent plant to ensure the seeds do not get destroyed by strong waves
• pneumatophores: root projection that stick out of soils to allow gaseous exchange via lenticels
• prop roots // underground cable root system: provide support against strong wind and waves.

Question 14

Define colonisation

Answer 14

The process of conquering a new habitat where no life existed previously.

Question 15

Why will Rhizophora sp. replace the Avicennia and Sonneratia sp.?

Answer 15

Avicennia and Sonneratioa sp. has prop roots which traps mud and sendiments causing the soil level to increase. This becomes less suitable for pioneer sp. and more suitable for Rhizophora sp. Succesion occurs

Question 16

What roots does Brugeria sp. have?

Answer 16

Buttress roots

Question 17

Explain the importance of mangrove ecosystem as a protection zone

Answer 17

• protects small fish, crabs and shrimps from predatora and strong wave current
• acts as natural barrier which reduces impacts of strong wind and waves

Question 18

Explain colonization and succession in a pond

Answer 18

• pioneer species of pond ecosystem is submerged plants
• they have fibrous roots which penetrate into the soil to obtain nutrients
• as submerged plants they and decompose, the organic matter and humus accumulates at the bottom of the pond makind the pond more shallow
• the pond is less suitable for submerged plants but more suitable for floating plants
• floating plants cover the surface of the pond preventing sunlight form penetrating across and reaching the submerged plants below
• submerged plants die and decompose to acculate the organic matter at the base of the pond
• the more shallower pond is less suitable for floating plants
• emergent plants grow from the side of the pond toward the centre making the pond more shallow
• less suitable for emergent plants and more suitable for land plants.
• As time passes, the pond becomes drier and woody, herbaceous plants, shrubs start to grow
• Jungle emerges

Question 19

How does food supply in an area affect the population ecology of an organism?

Answer 19

• important for heterotrophs which feed on other other organisms

Question 20

How does a random population distribution describe a species

Answer 20

species have little interactions with one another

Question 21

What kind of organisms would quadrant sampling technique be suitable to be used for?

Answer 21

• plants or organisms with minimal or slow movements

Question 22

The formula:
Number of quadrants containing studied species / number of quadrant used
is to determine _____

Answer 22

frequency of species

Question 23

What is the formula to determine density of studied species?

Answer 23

Total number of studied species in all quadrants / Total number of quadrants used x area of 1 quadrant

Question 24

What method is used to estimate population sixe of free moving organisms?

Answer 24

capture-mark-release-recapture-technique