4.1 Species, Communities, and Ecosystems

Question 1

Species

Answer 1

Group of organisms that can potentially interbreed to produce fertile, viable offspring.

Question 2

Hybrids

Answer 2

Offspring produced by crossbreeding, reproductively sterile. E.g. Liger, mule.

Question 3

Population

Answer 3

Group of organisms of the same species that are living in the same area at the same time.

EXTRA: Organisms that live in different populations are reproductively isolated and unlikely to interbreed, however, if interbreeding is functionally possible these organisms are classified as the same species.

Question 4

Community

Answer 4

Groups of populations that live and interact with each other in a given area

Question 5

Habitat

Answer 5

The environment in which a species usually lives, or the location of a living organism.

Question 6

Ecosystem

Answer 6

A community and the abiotic environment.

Question 7

Ecology

Answer 7

The study of relations between organisms as well as their environment

Question 8

Autotrophs

Answer 8

Producers - synthesis own organic molecules from simple inorganic substances - e.g. CO2, nitrates.

Energy for synthesis is derived from sunlight (photosynthesis) or oxidation of inorganic molecules (chemosynthesis)

Question 9

How is energy for synthesis is derived for Autotrophs

Answer 9

From sunlight (photosynthesis) or oxidation of inorganic molecules (chemosynthesis)

Question 10

Heterotrophs

Answer 10

consumers - obtain organic molecules from other organisms as they cannot produce their own organic molecules

Question 11

Name 3 different heterotrophs

Answer 11

1. Consumers
2. Detritivores
3. Saprotrophs

Question 12

Mixotrophs

Answer 12

Unicellular organisms that can use both forms of nutrition, depending on resources availability

Question 13

Example of mixotroph

Answer 13

Euglena gracilis

• chlorophyll for photosynthesis (autotrophic)
• feeds on detritus (heterotrophic)

Question 14

Consumers

Answer 14

ingest organic molecules found from living/recently killed organisms.

1. herbivores: cows.
2. carnivores: tiger.
3. Omnivores: humans, pandas

Question 15

Detritivores

Answer 15

ingest organic molecules found in the non-living remnants of organisms, e.g. detritus, humus, through internal digestion.

1. dung beetles
2. earthworms
3. snails
4. crabs

Question 16

Saptrotrophs

Answer 16

Organisms that live on/in non-living organic matter, secreting digestive enzymes to facilitate external digestion of nutrients. As saprotrophs facilitate the breakdown of dead organic material, they are commonly referred to as decomposers.

1. Bacteri
2. fungi
3. mushrooms
4. mold.

Question 17

Detritus

Answer 17

dead, particulate organic matter, e.g. decaying organic material and feces

Question 18

Humus

Answer 18

decaying lead litter intermixed within the topsoil

Question 19

Nutrients

Answer 19

Materials required by an organism - carbon, nitrogen, phosphorus.

As the supply of inorganic nutrients on Earth is finite, thus there is a limited supply as new elements cannot simply be created. Hence, chemical elements are constantly recycled

Question 20

Nutrient cycle

Answer 20

1. Autotrophs – synthesise inorganic nutrients into organic compounds.
2. Heterotrophs – ingest organic compounds from autotrophs for growth and respiration, releasing inorganic by-products.
3. Saprotrophs – decompose the remains of deceased organisms and inorganic material into the soil < ensuring a continual supply of raw materials for the autotrophs.

Question 21

3 main components required for sustainability in an ecosystem

Answer 21

1. energy availability
2. nutrient availability
3. recycling of wastes

Question 22

3 main components required for sustainability in an ecosystem (EXPLAINED)

Answer 22

1. Energy availability – e.g. light from sun provides initial energy source.
2. Nutrient availability – saprotrophic decomposers ensure consistent recycling.
3. Recycling of wastes – certain bacteria can detoxify harmful waste by-products, e.g. Nitrosomonas.

Question 23

What are mesocosms?

Answer 23

Enclosed environments that allow parts of a natural environment to be observed under controlled conditions.

E.G. Terrarium – a small transparent container where selected plants are observed.

Question 24

Quadrant sampling

Answer 24

A quadrat is a rectangular frame of known dimensions that can be used to establish population densities – placed inside a defined area in either random or according to a design. Not an effective method for counting motile organisms, mainly used for plants and sessile animals.

Question 25

Chi-squared tests

Answer 25

Can be applied to data generated from quadrat sampling to determine if there is a statistically significant association between the distribution of two species, at the 0.05 level.

(observed value - expected value)^2 / expected value = x^2

Question 26

0 association

Answer 26

there is no potential interaction between species in a given environment as they are independent of one another.

Question 27

+ association

Answer 27

typically found within the same habitat.

POSSITIVE ASSOCIATION: Predator-prey or symbiotic relationship.

Question 28

• association

Answer 28

typically do not occur within the same habitat

NEGATIVE ASSOCIATION: competition for the same resources

1. competitive exclusion
2. resource partitioning

Question 29

Competitive exclusion

Answer 29

1 species may utilise the resources more efficiently, precluding survival of the other species.

Question 30

Resource partitioning

Answer 30

both species alter use of the environment to avoid direct competition.