Sexual Selectionfo animals ( chitra ).pptx

Sexula selection by animals

1. Guided by - Mr. Subham Singh Sir GOVERNMENT E. RAGHAVENDRA RAO PG SCIENCE COLLEGE, BILASPUR (C.G.) Department of zoology Submitted by - Chitrakanta pendro M.Sc. III semester Roll no. - Topic – Sexual Selection

2. Introduction Sexual selection – proposed Charles Darwin (1817) It is a kind of natural selection in which membrane of one sex (female )choose mates on the basis of certain characteristics e.g. Large size , strength charm etc.

3. Sexual Selection (Intersexual selection or Female choise ) and membrane of the same sex (males) complex for mating with the females (male male competition). Hence , D arwins theory of sexual selection states that “ there will be a selection for the traits/characters that increase mating success”.

4. Examples – (1) Intersexual selection (male male competition ). - In many species the males with the greatest size , strength or best developed weapons achieve the highest mating success. - In Northern elephant seals (Mirououngr angustirostris) , the female elephant seal live in a group called Harem (It is a group of females sharing a single mate ). - The male elephant seals fight with each other to monopolize the Harem. - The largestand the strongest male wins and monopolize the Hamem .

5. (2) . Female choice / Intersexual selection - Suggested by Charles Darwin's that female choose for the most “ charming or agreeable “ males A classic experiment is done by Malte Andersson ( 1982) on the long -tailed widowbird (Euplectes peogne ) in Kinya . - In the male of these widowbirds , they possess a remarkable tail more than half a meter long . Female possess short tails . - Males defend territories to which they attract sexual females for mating . Males do not show their tails to others males for competition. - Males show their long tails to the females where a female passes by.

6. Why are females choosy ? - During last 40 years , sexual studies done to know what benefits females from choice - females get two broad types of benefits . 1. Good resources. 2. Good genes.

7. 7 Good resources In the case of long tailed widowbird female nest in the territories of their chosen male , so choice increase their access to good resources. - So, the choice of male traits e.g., long tail, can be due to resources (nest site or food that improves a females reproductive success . Example- The male North American Bullfrogs (Rana catesbeiana) defend their territories in ponds / lakes where females come to lay eggs .

8. 8 Females prefer the territories which are better for survival of eggs and protect by males and largest and strongest male gains the best site. Hence, female choice and male male competition go hand – in – hand.   In some other cases , female choose the males on the basis of their ability to provide food.

9. 9 In the case of hanging flies ( Hylobaittcus apicalis ),the female fly with mate the male fly ONLY if hi provides a Large insect for her to eat during copulation. It is called as Nuptial gift ( it is a nutritional gift given by one partner during mating to other partner.

10. References https://www.youtube.com https://www.google.com https://www.wikipedia.org

11. Thank you