3.2.1C - Niches and Keystones

Question 1

what is an ecological niche?

Answer 1

• the ecological niche can be defined in terms of habitat, feeding relationships and interactions with other species
• the role and space that an organism fills in an ecosystem, including all its interactions with the biotic and abiotic factors of its environment

Question 2

what are the two components used to identify ecological niches?

Answer 2

1. distributional component - a habitat a species occupies as a function of its physiological and behavioral attributes (i.e. its adaptations)
2. functional component - the role a species plays in the community, in terms of its trophic level

Question 3

what are the two types of ecological niche?

Answer 3

1. fundamental niche - all the potential resources that a species can use in its environment. Requires the absence of competition
2. realised niche - some habitats and resources are not available because competitors occupy them. This is what the species actually uses

Question 4

how do you identify a fundamental vs realised niche on a graph?

Answer 4

• realised niches are narrower than fundamental niches, therefore the species occupies a narrower range of habitats than it would in the absence of competition
• the realised niche can be regarded as a ‘competitive refuge’

Question 5

what is the competitive exclusion principle?

Answer 5

• two species competing for the exact same limited resource cannot stably coexist
• when one species has even the slightest advantage over another, the one with the advantage will dominate in the long term
• this leads either to the extinction of the weaker competitor or to an evolutionary or behavioral shift towards a different ecological niche

Question 5

how can niche partitioning solve the problem of competitive exclusion?

Answer 5

• also known as niche segregation, niche separation and niche differentiation
• this is where the niche is divided, so all competing species use the environment differently in such a way that helps them to coexist and therefore survive

Question 6

define keystone species

Answer 6

• a plant or animal that plays a unique and crucial role in the way an ecosystem functions
• keystone species are those that are known to have an influence on an ecosystem that is disproportionate to their abundance

Question 7

recall 2 examples of keystone species

Answer 7

1. cassowary - eats native fruits and disperses the seeds of more than 60 species around the forest via its faeces –> forest regeneration
2. Northern Quoll - eats many insects, frogs, mammals, cane toads –> consumption helps to maintain balance in ecosystem

Question 8

ensure you understand the below exam question: