4.1 Species, communities and ecosystems

Question 1

Species

Definition

Answer 1

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

Question 2

Habitat

Definition

Answer 2

The environment in which a species normally lives.

Or: the location of a living organism.

Question 3

Population

Definition

Answer 3

A group of organisms of the same species who live in the same area at the same time.

• Organisms that live in different regions (i.e. different populations) are reproductively isolated and unlikely to interbreed, however are classified as the same species if interbreeding is functionally possible

Question 4

Community

Definition

Answer 4

A group of populations living and interacting with each other in an area.

Question 5

Ecosystem

Definition

Answer 5

A community and its abiotic environment.

Abiotic: the non-living components (water, soil, temperature, nutrients)

Question 6

Autotrophs

Definition

Answer 6

Organisms that synthesize their organic molecules from simple inorganic substances (e.g. CO₂) found in the abiotic environment.
- The energy for this process is generally derived from sunlight (photosynthesis) or via the oxidation of inorganic molecules (chemosynthesis)
- Are commonly to as producers

Question 7

Heterotrophs

Definition

Answer 7

Organisms that obtain organic molecules from other organisms

Within heterotrophs there are: consumers, detritivores and saprotrophs

Question 8

Consumers

Definition

Answer 8

Ingest organic molecules from living or recently killed organisms

Are heterotrophs.

Question 9

Detritivores

Definition

Answer 9

Ingest organic molecules found in the non-living remanants of organisms (e.g. detritus, humus)

Are heterotrophs.

Question 10

Saprotrophs

Definition

Answer 10

Release digestive enzymes and then absorb the external products of digestion (decomposers)
- External digestion

Are heterotrophs.

Question 11

Nutrient Cycling

What are nutrients? What’s the supply of nutrients?

Answer 11

• Nutrients refer to the material required by an organism (carbon, nitrogen, phosphorus)
• The supply of inorganic nutrients on Earth is finite (limited in supply)
• Therefore, the supply of inorganic nutrients is maintained by nutrient cycling.

Question 12

Nutrient cycle

How does it function?

Answer 12

• Autotrophs: convert inorganic nutrients (from the air water and soil) to organic compounds
• Heterotrophs: ingest these organic compounds and use them for growth and respiration, releasing inorganic byproducts
• When organisms die, saprotrophs decompose the remains and free inorganic materials into the soil
• The return of inorganic nutrients into the soil ensures the continual supply of raw materials for the autotrophs

Question 13

Diferent levels of an ecosystem from smallest to biggest

Answer 13

Species –> Population –> Community –> Ecosystem

Question 14

Can ecosystems be sustainable over long periods of time?

Answer 14

Yes, they are largely self-contained and have the capacity to be self-sustaining over long periods of time.

Three main components required for sustainability in an ecosystem:
- Energy availability: light from the sun provides the initial energy source for almost all communities
- Nutrient availability: saprotrophic decomposers ensure the constant recycling of inorganic nutrients within an environment
- Recycling of wastes: ertain bacteria can detoxify harmful waste byproducts

Question 15

Mesocosms

Answer 15

Mesocosms are enclosed environments that allow a small part of a natural environment to be observed under controlled conditions.
- A terrarium is a small transparent container (e.g. glass or plastic) in which selected plants (or animals) are kept and observed