topic 5: ecosystems, succession, & speciation and evolution

define Evolution

a change in the heritable traits of biological populations over successive generations.

explain evolution

• new alleles arise as a result of gene mutations that give rise to variation within species

• a change in environment leads to a change in selection pressures which in turn makes some alleles more desirable then others

• therefore, possessing some alleles enables organisms to survive and reproduce and consequently, the frequency of such alleles increases as they’re passed down to offsprings

define speciation

the process by which new species arise after a population becomes reproductively or geographically isolated and cannot interbreed.

What is meant by allopatric speciation?

geographic barrier separates populations → no gene flow → different selection pressures → eventual reproductive isolation

What is meant by sympatric speciation?

no geographic barrier; reproductive isolation occurs within the same area via behavioural, mechanical, temporal, or genetic changes

What are biofuels?

fuels which have been made from biomass

define succession

the change of 1 community of organisms into the other.

describe primary succession

The area is first colonized by the pioneer species, such as lichens, which are adapted to survive in such harsh conditions. As they die, they are decomposed by microorganisms, adding humus which leads to the formation of soil which makes the environment less hostile, more suitable for more complex organisms. Over time, the soil becomes richer in minerals, enabling larger plants to survive. Eventually, a climax community is established.

define intraspecific competition

competition between members of the same species within the same niche for a limited resource

define interspecific competition

is competition between members of different species within a community for the same resource, the niches overlap