1. Module 8

1.26. Page 3

Lesson 6: Page 3

Module 8—Populations, Individuals, and Gene Pools

 

Lesson Summary

 

In Lesson 6 you focused on answering the following question:

  • What are the defence mechanisms within predation and competition?

All species rely on defences of some kind to increase their chances of survival. Defences can take the following forms:

  • structural characteristics (e.g., thorns, claws)
  • chemical characteristics (e.g., plant toxins, venoms)
  • behaviours (e.g., territoriality, roaring)
  • colouration (e.g., protective colouration, mimicry, and cryptic colouration)

These defences allow organisms to compete intraspecifically against others in their own species for survival. The best competitors, those with superior defences, will live to pass the genes for these successful defences to the next generation, thereby improving the population’s gene pool.

 

Interspecific competition occurs when organisms from two different species are both attempting to fill a trophic level. If there is no scarcity, both species may in fact share the niche. However, competition and the defences that allow an organism to compete well, only become important during periods of scarcity. Lack of food, water, space, and other resources means that nature must select a few winners from many competitors, and it is then that gene pool change occurs.

 

Lesson Glossary

 

Consult the glossary in the textbook for other definitions that you may need to complete your work.

 

behavioural defences: actions and gestures that are meant to communicate that the organism is dangerous and should be avoided or is harmless and not threatening

 

chemical defences: toxic, bad-tasting, or bad-smelling chemicals secreted by an organism that either discourage consumers from eating it, poison consumers, or prevent competitors from growing or living nearby

 

cryptic colouration (camouflage): colours or patterns that allow an organism to blend into its environment and avoid being seen

 

interspecific competition: when members of two different species compete for scarce resources and survival; competition only occurs when there are too many organisms and not enough resources

 

intraspecific competition: when members of the same species compete against each other for scarce resources and survival; causes microevolution because one phenotype or allele will have better survival than another

 

The scarcer the resources, the more extreme the competition and the faster microevolution occurs.

 

mimicry: when a harmless organism has the same bright colouration of an organism that has protective colouration

 

niche: a position or role taken by an organism within its community

 

protective colouration: bright colours that give clear warning to potential attackers

 

structural defences: physical parts of the organism that either protect the organism from being consumed or allow the organism to compete better for scarce resources