Ecology

Question 1

Ecology

Answer 1

Study of interactions between living organisms and their environment

Question 2

Abiotic (non-living environment)

Answer 2

Consists of chemical and physical factors
e.g. light intensity, temperature, water, air, pH of soil and water

Question 3

Biotic (living environment)

Answer 3

Consists of all living things that are part of the organism’s environment, which it interacts with

Question 4

Species

Answer 4

A group of organisms that can potentially interbreed and produce fertile offspring

Question 5

Population

Answer 5

A group of organisms of one species that can interbreed and live in the same environment at the same time

Question 6

Community

Answer 6

Different populations of plants and animals that live and interact in a particular environment

Question 7

Ecosystem

Answer 7

Made up of physical interactions between a community and physical environment

Question 8

Biosphere

Answer 8

The portion of the earth where all life exists

Question 9

Interactions

Answer 9

Vital part of how organisms develop and change over time
1. Commensalism
2. Mutualism
3. Parasitism
4. Predatiom

Question 10

1. Commensalism

Answer 10

r/s between two organisms where one receives a benefit or benefits from the other and the other is not affected by it

Question 11

Example 1

Answer 11

Whale and barnacles
Barnacles need a place to anchor and wait for food to come their way. They benefit by attaching to the whale, allowing them to move through waters. The whale receives no benefit, but is not harmed either

Question 12

Example 2

Answer 12

Long tailed macaques and greater racket-tailed drongos
The drongos follow the trails of troops of macaques to eat the insects that these monkeys stir up in their wake as they move in the tree canopies

Question 13

2. Mutualism

Answer 13

Interaction between two organisms where both benefit from the interaction

Question 14

Example 1

Answer 14

Pollination
Plant gets benefit from dispersal of pollen. Pollinator obtains nectar from the flower where their young larvae can hatch safely

Question 15

Parasitism

Answer 15

Non-mutual r/s between species, where one species, the parasite, benefits at the expense of the other, its host
Parasites that live on their host are called ectoparasites
Those that live inside their host are called endoparasites

Question 16

Example 1 (Ectoparasites)

Answer 16

Fleas
Fleas live on larger animals, like cats, dogs and deer

Question 17

Example 2 (Endoparasites)

Answer 17

Flukes
Found in blood vessels of intestine. Produce larvae which penetrate skin and blood vessels of humans

Question 18

Predation

Answer 18

r/s where one organism captures and consumes the other

Question 19

Example 1

Answer 19

Bats eating insects
Snakes eating rodents
Tigers eating wild boars

Question 20

Predation and population dynamics

Answer 20

Increasing pop. size of prey will result in corresponding increase in pop. size of predator; predator has more food – and vice versa
Predator-prey interactions sometimes result in pop. cycles, where both predator and prey pop.s undergo regular increases and decreases, but the cycles are out of phase with one another

Question 21

Examples of r/s between diff. organisms

Answer 21

1. Parasitism
   Only tapeworms benefit from obtaining nutrients from their hosts. Tapeworms do not benefit the host but instead harm the host by weakening it
2. Mutualism
   Bess obtain nectar from flowers as a source of food. in doing so, bees help the plant pollinate its flowers, allowing it to reproduce. Both the bees and flower benefit from this r/s
3. Parasitism
   Only aphids benefit by obtaining a constant source of nutrients. The host plant loses nutrients that are needed for its own growth and reproduction

Question 22

Producers

Answer 22

They are the autotrophs that manufacture glucose from carbon dioxide using light during photosynthesis. Examples include green plants, photosynthetic bacteria, green, brown or red algae.

Question 23

Consumers

Answer 23

Heterotrophs that feed directly on producers are known as primary consumers or herbivores. Those that depend indirectly on producers by feeding on primary consumers are known as secondary consumers or carnivores. Those that feed on secondary consumers are tertiary consumers and so on.

Question 24

Decomposers

Answer 24

Decomposers break down dead plants, animals and the waste of other organisms. They are very important for any ecosystem. When plants and animals die, they become food for the decomposers, such as bacteria, fungi and earthworms. Decomposers recycle dead plants and animals into chemical nutrients like carbon and nitrogen that are released back into the soil, air and water.

Question 25

Processes involved in maintains a stable ecosystem

Answer 25

Photosynthesis and respiration are processes that ar involved in the flow of energy through food chains and food webs. Nutrients trapped in living organisms are recycled within the environment. Energy flows through food chains and food webs and processes like photosynthesis and respiration are involved. Nutrients in organisms are recycled within the environment through the actions of decomposers.

Question 26

Food chain

Answer 26

A food chain shows the transfer of energy and materials from organism to organism along a feeding pathway. Each stage in a food chain e.g. producer is known as a tropic level. The arrows in a food chain indicate the direction of energy flow.

Question 27

Food web

Answer 27

A food web happens when more than one organism can be present at each tropic level. E.g. all herbivores are at same tropic level of primary consumer. Each species very often feeds on more than one type of prey, and each species also may be food for at least two or more predator species.

Question 28

Compared to food chains, food webs are:

Answer 28

• more stable
• more resistant to disruption

Question 29

Tropic level

Answer 29

A tropic level is a stage in a food chain at which organisms obtain their food in the same general manner.

Question 30

Pyramid of Number & Biomass (must know but don’t need memorise unless indicated with asterisk)

Answer 30

Number of organisms in a food chain can be represented graphically in a pyramid. Each bar represents the number of individuals at each tropic level (feeding level) in the food chain.
*pyramid of numbers usually show that number of organisms at each trophies level gets smaller towards the top and at the same time, there is an increase in the body size of the animal. This representation and be calculating the biomass of each tropic level

Question 31

Biomass pyramid

Answer 31

*calculated by mass of each individual x the number of individuals; at each tropic level per unit at a given time in the community

Question 32

Difference in pyramids

Answer 32

Pyramid of numbers show the number of organisms at each tropic level, while pyramid of biomass shows the mass of organisms at each tropic level. E.g. for pyramid of numbers, oak tree has smallest base while for pyramid of biomass, oak tree has the broadest base, this is because the pyramid of numbers does not take into consideration the biomass of each organism, for the pyramid of biomass, the large biomass of one oral tree is able to support a large number of insects.
Pyramid of energy looks similar to pyramid of biomass as energy is lost from one tropic level to another; energy decreases as we go up the trophic levels.

Question 33

Flow of energy in a food chain

Answer 33

Only some energy is available to the next organism in the food chain — energy is lost as heat cannot be converted into other forms of energy by living organisms. Thus, what is lost from ecosystems.
Only about 10% of what is ingested by a consumer is available to be passed on to the next trophic level of the food chain, the remaining 90% of energy is lost as heat and waste.

Question 34

Energy transfer in a food chain

Answer 34

• Chemical energy from food is oxidases during respiration to release energy for cell activities
• Most energy is lost as heat energy
• Heat energy does not return to the Sun or re-enter an organism
• Energy flow is one way
• Known as non-cyclical flow of energy. Energy transfer in a food chain is unidirectional

Question 35

Pyramid of energy

Answer 35

Primary producers have largest base as they introduce energy into the ecosystem.

Question 36

Reasons for loss of energy

Answer 36

1. Not all the food is ingested e.g. herbivores — cellulose and woody xylem tissues; leftover food
2. Energy is utilised to drive life activities (respiration, cell division & growth)
3. Heat energy is lost to the environment during respiration

Question 37

How is energy lost from consumers to surroundings

Answer 37

1. Energy is lost as heat to the surroundings during respiration
2. Energy is lost as waste products in undirected food
3. Not all food is ingested and some are left behind

Question 38

A food chain has four trophic levels. Suggest why it will not be feasible for this food chain to have another trophic level.

Answer 38

The amount of energy transferred along the food chain becomes progressively less. Thus, the energy available to the organism in another trophic level will be insufficient for its needs.