4.1 species communities ecosystems

Question 1

what consitutes a species?

Answer 1

group of organisms that can potentially interbreed to produce fertile, viable offspring
- hybrids: offspring off 2 different species; reproductively sterile

Question 2

what constitutes a population?

Answer 2

group of organisms of the same species that are living in the same area at the same time
- organisms that live in diff regions (diff populations) are reproductively isolated; unlikely to interbreed; but if interbreeding is functionally possible they are same species; basis for divergent evolution

Question 3

what constitutes a community?

Answer 3

group of populations living together and interacting with each other within a given area

Question 4

what constitutes a habitat?

Answer 4

the environment in which a species normally lives / location of a living organism

Question 5

what constitutes an ecosystem?

Answer 5

a community (group of populations living together and interacting with each other within a given area) and its abiotic environment

Question 6

what is ecology?

Answer 6

the study of relationships between living organisms / between organisms and their environment

Question 7

what are the different modes of nutrition of living organisms?

Answer 7

all organisms require organic molecules such as amino acids to carry out functions of life

• autotrophs: produce their own organic molecules using light energy / energy derived from oxidation of chemicals
• heterotrophs: obtain organic molecules from other organisms (consumers, detritivores, saprotrophs)
• mixotrophs: mix of both

Question 8

what are autotrophs?

Answer 8

• synthesise their own organic molecules from inorganic substances e.g. CO2, nitrates
• energy for this process derived from sunlight (photosynthesis) / oxidation of inorganic molecules (chemosynthesis)
• commonly referred to as producers

Question 9

what are heterotrophs?

Answer 9

• obtain organic molecules from other organisms
• cannot produce their own organic molecules: consumers
• consumers, detritivores, saprotrophs

Question 10

what are mixotrophs?

Answer 10

• use both modes of nutrition, depending on resource availability
• certain unicellular organisms

Question 11

what are consumers?

Answer 11

ingest organic molecules from living (herbivores, omnivores, carnivores) / recently killed organisms (scavengers)

Question 12

what are detritivores?

Answer 12

ingest organic molecules found in non-living remains of organisms e.g. detritus, humus

Question 13

what are saprotrophs?

Answer 13

secrete digestive enzymes and absorb external products of digestion; decomposers

Question 14

what is nutrient cycling and what are the different roles that organisms play?

Answer 14

• nutrients: material required by organisms
• elements like carbon, nitrogen, phosphorus
• supply of inorganic nutrients is finite –> hence have to be constantly recycled

1. autotrophs: obtain inorganic nutrients from the air, water and soil and convert them into organic compounds
2. heterotrophs: ingest organic compounds and use them for growth and respiration, releasing inorganic byproducts
3. saprotrophs: decompose dead remains and free inorganic materials into soil
4. return of inorganic materials to soil ensures continuing availability of nutrients for autotrophs

Question 15

how do ecosystems remain self-sustainable for long periods of time?

Answer 15

• largely self-contained and self-sustaining over long periods of time
• 3 main components required for sustainability in ecosystem
  1. energy availability: steady source of energy; light energy from sun provides initial energy source for almost all communities
  2. nutrient availability: from nutrient cycling; saprotrophic decomposers ensure constant recycling of inorganic nutrients within environment
  3. recycling of waste materials: certain bacteria can detoxify harmful waste byproducts

Question 16

what do the different chi-squared test results mean?

Answer 16

• positive association: species found in same habitat
• negative association: species occur separately in differing habitats
• no association: species occur as frequently apart as together