C1 Species and Communities

Question 1

What is a limiting factor?

Answer 1

A component of an ecosystem which limits the distribution or numbers of a population - can be biotic or abiotic

Question 2

Factors affecting the distribution of plant species

Answer 2

temperature, water, light (intensity/wavelength), soil pH, soil salinity, mineral nutrient availability

Question 3

Factors affecting the distribution of animal species

Answer 3

Temperature, water, breeding sites, food supply, territory/habitat

Question 4

Low temperature adaptation in plants - EXAMPLE

Answer 4

Woody species of plants (Oak and Maple trees) synthesise antifreeze proteins which prevents formation of ice crystals inside cells, allowing them to survive in temperatures as low as -40 degrees. Cannot survive in high temperatures as they transpire readily

Question 5

Migration for food supply - EXAMPLE

Answer 5

Southern right whales migrate from Antarctic feeding areas to temperate breeding areas along coasts of Chile, Southern Africa, Australia, which is fuelled entirely by fat accumulated during their 4-month feeding stay - travel 2,500km each way

Question 6

Territory availability and distribution of animals - EXAMPLE

Answer 6

Tigers require large territories and these are mainly located in forests, to shelter their prey and have access to water. These territories are marked with urine and faeces. Increased human populations has decreased the habitat size, causing max population size of tigers to decrease.

Question 7

What is a keystone species

Answer 7

A species that has a disproportionately large impact on the environment relative to its abundance - not the dominant species within a community and don’t have to be apex predators

Question 8

How do keystone species influence communities

Answer 8

Predators - can exert pressure on lower trophic levels to prevent them from monopolising certain resources
Mutualism - can support life cycle of various species within a community
Engineers - can refashion environment in a way that promotes survival of other species

Question 9

Examples of keystone species

Answer 9

Sea stars (predators) - prey on urchins and mussels
Honey bees (mutualist) - pollinate wide variety of plant species
Beavers (engineers) - build dams that transform environment

Question 10

What is an ecological niche

Answer 10

describes the functional position and role of an organism within its environment - has various components:
- habitat
- activity patterns
- resources
- interactions with other species

Question 11

Herbivory

Answer 11

Act of eating only plant matter:
Can be harmful or beneficial to the plant species as a whole (certain types of betle may feed voraciously on the leaves of crops, causing crop failure BUT fruit-eating animals spread seeds from fruit through faeces, promoting seed dispersal)

Question 12

Predation

Answer 12

Biological interaction where one organism hunts and feeds on another organism:
- if prey population decreases, predator numbers decrease as intra-specific competition increases
- if prey population increases, predator numbers increase because over-abundance of food source

Question 13

Symbiosis

Answer 13

Close and peristent interaction between 2 species (can be obligate - required for survival - or facultative - advantageous without being necessary)
Mutualism - both species benefit
Commensalism - one species benefits, other is unaffected
Parasitism - one species benefits to detriment of the other species

Question 14

Interspecific competition within a shared niche

Answer 14

The less well-adapted species will struggle to survive and eventually be eliminated from niche
2 responses: Competitive exclusion or resource partitioning

Question 15

Shelford’s law of tolerance

Answer 15

Useful tool to understand relative abundance of a species and predict community structure

Question 16

Black Mangrove - zones of tolerance, stress, intolerance

Answer 16

Optimal zone for growth in salinity levels of 24-48 ppt
Outside this range mangrove experiences zones of stress

Question 17

Zooxanthellae - zones of tolerance, stress, intolerance

Answer 17

Have optimal growth range in water temperatures between 20-30 degrees
When zooxanthellae leave coral polyps, during zones of stress, there is coral bleaching

Question 18

Symbiotic relationship between zooxanthellae and reef-building coral species

Answer 18

mutualistic relationship, zooxanthellae provide the unique and beautiful colours of many corals
coral provides algae with a protected environment and algae provides coral with oxygen, products of photosynthesis and helps it remove waste
when there are environmental conditions the zooxanthellae leave the coral, causing coral bleaching

Question 19

Fundamental niche

Answer 19

Entire set of conditions under which an organism can survive and reproduce - theoretical habitat

Question 20

Realised niche

Answer 20

Set of conditions used by an organism after including interactions with other species - actual habitat that is completely occupied by an organism in the presence of competing species

Question 21

Use of quadrats for population sampling

Answer 21

with this technique you can compare populations of different species in same area or populations of same species in different areas
must be random sampling, and have clear borders with randomly selected coordinates

Question 22

Using transects for population sampling

Answer 22

Used to estimate species distribution over a set distance and in correlation with abiotic variables - kite graph used to represent distribution data
quadrats are placed at regular intervals and populations/abundance of each species recorded at each point