Question

1. Define and contrast sexual selection and natural selection, and briefly discuss the primary factors driving sexual selection

2. Briefly describe the most fundamental assumption made by people who do phylogenetic systematics (hint – the assumption is based on fact)

Answer 1

ANSWER 1:

Definition of sexual selection- Sexual selection is a kind of natural selection in which one member of a particular sex of a species choose its mate of other counterpart sex to mate with. Two types of sexual selection are - Intrasexual selection or competition and Intersexual selection.

Intrasexual selection- These usually occurs between males of the same sex, for mating with their respective partners.

Intersexual selection- These usually occurs between members of one sex, usually females choose members of the opposite sex.

Definition of natural selection- It is one of the vital mechanism of evolution. It is the process where organism with favourable trait are more likely to survive and reproduce, so that these traits are passed on to next generation.

Point of difference	Sexual selection	Natural selection
1.Influence	Sexual selection theory is mainly influenced by mating preferences.	Natural selection theory is influenced by better adapted traits that tend to survive in next generations
2. Type of struggle	Sexual struggle.	Struggle for existence
3.Differentiation	Among particular members of same sex	Irrespective of sex, among the conspecifics.
4. Selection	Mate choice, same-sex combat	The environment including other species.

5. Example

Colourful tail feathers of peacock.

Giraffe Neck vertebrates evolution.

ANSWER 2: The most fundamental assumptions of phylogenetic systematics:-

(i) Any group of organisms are related by descent from single common ancestors, because homologous sequences must be derived from common ancestor.

(ii)Characteristic of the species changes occur in lineages over a period of time.

(iii) There is a branching pattern or bifurcating pattern of lineage.