4.1 Species communities and ecosystems

Question 1

Species

Answer 1

is a group of organisms that can interbreed to produce fertile offspring

If species are not closely related it is often impossible for individuals of the different species to breed.

Question 2

If members of two closely related species do interbreed (or cross-breed) and produce offspring …

Answer 2

the hybrids will be sterile e.g. mules.

Question 3

Population

Answer 3

s a group of organisms of the same species that are living in the same area at the same time.

Question 4

If organisms of the same species are geographically separated:

Answer 4

they are unlikely to interbreed with each other – this does not mean that they are different species. If they have the potential to interbreed, they are still the same species.

Question 5

If two populations of the same species never interbreed:

Answer 5

then they may gradually develop differences that prevent them from interbreeding. In this case, they may develop into unique species if they lose the ability to interbreed and produce fertile offspring.

Question 6

Reproductive isolation:

Answer 6

occurs when barriers are mechanisms prevent two groups from interbreeding, keeping their gene pools separate from each other

temporal, geographical, behavourial

Question 7

All organisms require organic molecules, such as amino acids and glucose, to:

Answer 7

carry out the functions of life, for example metabolism, growth, and reproduction.

Question 8

Autotrophs

Answer 8

synthesize their own organic molecules and are therefore known as producers

Question 9

Heterotrophs

Answer 9

however obtain their organic molecules from other organisms

Question 10

A few plants and algae use a combination of different modes of nutrition and are hence known as

Answer 10

mixotrophs

Question 11

Venus flytrap (Dionaea muscipula)

Answer 11

is found in subtropical wetlands and like most plants photosynthesise (autotroph), but also traps and digests both insects and spiders (heterotroph), to compensate for the nutrient poor soil of the wetlands.

Question 12

Euglena sp.

Answer 12

is a genus of Algae that will photosynthesise (autotroph) in sufficient light, feeding as an autotroph, but can also ingest particles of food by phagocytosis, which it then digests (heterotroph)

Question 13

Consumers

Answer 13

feed off other organisms that are alive or recently dead.
Alive – mosquito sucking blood
Dead – lion feeding on killed gazelle

Question 14

Consumers ingest and digest their food:

Answer 14

Unicellular – e.g. Paramecium – ingest via endocytosis and digest in vacuole
Multicellular – e.g. Lion – ingest via mouth and digest via digestive system

Question 15

Consumers can be divided based on trophic groups according to what organisms they consume:

Answer 15

Primary consumers – feed on autotrophs
Secondary consumers – feed on primary consumers
Etc…
Most consumers can fit into a variety of trophic levels depending on what they consume

Question 16

Herbivores

Answer 16

feed on producers (e.g. deer, zebra and aphids)

Question 17

Omnivores

Answer 17

feed on a combination of both producers and consumers (e.g. chimpanzee, mouse)

Question 18

Carnivores

Answer 18

feed on other consumers (e.g. lions, snake and ladybirds)

Question 19

Scavengers

Answer 19

are specialised carnivores that feed mostly on dead and decaying animals (e.g. hyenas, vultures crows)

Question 20

Detritivores

Answer 20

are a type of heterotroph that obtain nutrients by consuming non-living organic sources, such as detritus and humus

Question 21

Examples of detritivores include

Answer 21

dung beetles, earthworms, woodlice and crabs

Question 22

Humus

Answer 22

decaying leaf litter mixed with the soil

Question 23

Detritus

Answer 23

dead, particulate organic matter. This includes decaying organic material and fecal matter

Question 24

Saprotrophs

Answer 24

live on, or in, non-living organic matter. They secrete digestive enzymes on to the organic matter and absorb the products of digestion.

unlike most heterotrophs, saprotrophs are not consumers, as they do not ingest food: digestion is external as enzymes are secreted.

Question 25

Because saprotrophs facilitate the breakdown of organic material, they are referred to as

Answer 25

decomposers

Question 26

Community

Answer 26

made up of groups of populations that are living and interacting together in the same area at the same time

All species are dependent on each other for survival
E.g. prey, food source, nutrient cycling, pollination

Communities also include plants and microbes; communities can contain 1000s of species

Question 27

Quadrat sampling can be used in a number of ways including:

Answer 27

Estimation of population density/size
Measuring the distribution of species

Question 28

Quadrats are

Answer 28

placed repeatedly in a sample area to provide a reliable estimate. Quadrats can be placed systematically, e.g. in a ‘belt transect’, typically to measure changing distribution, or randomly, e.g. to estimate population density. Depending on what is being measured either presence/absence, frequency or % coverage of a given species can be recorded. Both systematic and random sampling methods are used to avoid bias in the selection of samples.

Question 29

limitation of quadrat sampling

Answer 29

large and mobile animals cannot be effectively sampled. It is most suitable for plants and small, slow moving animals.

Question 30

Ecosystem

Answer 30

interaction of the community with its abiotic environment

Question 31

Abiotic environment can heavily influence communities:

Answer 31

Wave action on a rocky shore
Steep cliffs influence bird nesting

Question 32

Living organisms can influence abiotic environment:

Answer 32

Plants stabilize soil on coast lines and river beds

Question 33

all autotrophs…

Answer 33

convert CO2 from atmosphere or dissolved water into organic compounds

Question 34

Heterotrophs

Answer 34

obtain C and N as part of carbon compounds from their food, as well as inorganic nutrients from their abiotic environment (e.g. Na, K, Ca)

Question 35

nutrients

Answer 35

Elements required by an organism for growth and metabolism are regarded as nutrients, e.g. carbon, nitrogen and phosphorous.

The supply of nutrients is limited and therefore ecosystems constantly recycle the nutrients between organisms.

Question 36

Autotrophs nutrients

Answer 36

convert nutrients from inorganic form into organic molecules, e.g. carbon dioxide becomes glucose

Question 37

Heterotrophs nutrients

Answer 37

ingest other organisms to gain organic forms of nutrients

Question 38

saprotrophs nutrients

Answer 38

breakdown organic nutrients to gain energy and in the process release nutrients back into inorganic molecules, e.g. fungi release nitrogen as ammonia into the soil. This ensures the continuing availability of nutrients to autotrophs.

Question 39

sustainable

Answer 39

if it can continue indefinitely (forever).

Question 40

To remain sustainable an ecosystem requires:

Answer 40

Continuous energy availability, e.g. light from the sun
Nutrient cycling - saprotophs are crucial for continuous provision of nutrients to producers
Recycling of waste – certain by products of metabolism, e.g. ammonia from excretion, are toxic. Decomposing bacteria often fulfill this role by deriving energy as toxic molecules are broken down to, simpler, less toxic molecules.

Question 41

Mesocosms

Answer 41

biological systems that contains the abiotic and biotic features of an ecosystem but are restricted in size and/or under controlled conditions.