What is Intersexual Selection?

S6-SA5-0354

Grade Level:

Class 10

AI/ML, Physics, Biotechnology, Space Technology, Chemistry, Engineering, Medicine

Definition

What is it?

Intersexual selection is a type of natural selection where one sex (usually females) chooses mates based on certain desirable traits in the other sex (usually males). It's like choosing the best player for your cricket team, but for reproduction!

Simple Example

Quick Example

Imagine you are picking a gift for your friend. You choose the gift that looks the most attractive or useful, right? Similarly, in intersexual selection, one sex 'chooses' a partner with the most attractive features, like a peacock's colourful tail.

Worked Example

Step-by-Step

Let's say there are three male birds: Bird A has a very bright, colourful feather. Bird B has a dull feather. Bird C has a slightly bright feather.---Female birds prefer mates with bright feathers because it often signals good health.---Most female birds will choose to mate with Bird A.---Some might choose Bird C.---Very few, if any, will choose Bird B.---Over time, the genes for bright feathers will become more common in the bird population because Bird A and C reproduce more successfully.---This shows how the 'choice' of one sex (females) drives the evolution of traits (bright feathers) in the other sex (males).

Why It Matters

Understanding intersexual selection helps us in Biotechnology to study animal breeding and conservation. In Medicine, it can shed light on genetic predispositions and reproductive health. Even in AI/ML, similar 'selection' principles are used to train algorithms to pick the best features, like choosing the best product recommendations for you.

Common Mistakes

MISTAKE: Thinking intersexual selection is only about physical attractiveness. | CORRECTION: While physical traits are common, intersexual selection can also be based on behaviours like building a strong nest, performing a complex dance, or providing food.

MISTAKE: Confusing intersexual selection with intrasexual selection. | CORRECTION: Intersexual selection is about CHOICE by one sex, while intrasexual selection is about COMPETITION BETWEEN individuals of the SAME sex (e.g., two males fighting for a female).

MISTAKE: Believing only females make choices. | CORRECTION: While females often do the choosing, in some species, males can also be the choosier sex, selecting females based on certain traits.

Practice Questions

Try It Yourself

QUESTION: A male frog sings a very loud and clear croak. Female frogs prefer to mate with males that have the loudest croaks. Is this an example of intersexual selection? | ANSWER: Yes, because the females are choosing mates based on a specific trait (loud croak) in the males.

QUESTION: In a certain fish species, males with larger, more colourful fins are more likely to attract mates. If a fisherman only catches fish with small fins, how might this impact the fish population over time due to intersexual selection? | ANSWER: If males with small fins are removed, then males with larger, more colourful fins will have less competition and are even more likely to be chosen by females. This would lead to an increase in the proportion of fish with large, colourful fins in future generations.

QUESTION: Imagine a species of bird where males build elaborate nests. Females inspect these nests and choose mates based on the quality and size of the nest. If a disease makes it harder for males to gather nesting materials, what might be the long-term effect on the average nest quality and the number of offspring produced in the population? | ANSWER: The average nest quality would likely decrease over time because males cannot gather enough materials. This would make it harder for females to find high-quality nests, potentially leading to fewer successful matings and a decrease in the overall number of offspring produced in the population.

MCQ

Quick Quiz

Which of the following is the best example of intersexual selection?

Two male deer fighting with their antlers for access to females.

A female peacock choosing a male with the largest, most vibrant tail feathers.

A group of ants working together to build a large nest.

Plants producing more seeds in a favourable environment.

The Correct Answer Is:

Option B is correct because it describes one sex (female peacock) choosing a mate based on a specific trait (large, vibrant tail) in the other sex. Option A is intrasexual selection (competition), and C and D are not examples of sexual selection.

Real World Connection

In the Real World

Understanding intersexual selection is crucial in wildlife conservation efforts in India. For example, forest officials and biologists studying endangered species like the Great Indian Bustard need to understand what traits females look for in males to ensure successful breeding programs and maintain genetic diversity, helping these rare birds thrive.

Key Vocabulary

Key Terms

SEXUAL SELECTION: A type of natural selection where individuals with certain inherited traits are more likely to obtain mates. | TRAIT: A specific characteristic or feature of an organism. | REPRODUCTION: The process by which living organisms produce new individuals of their own kind. | GENES: Units of heredity passed from parents to offspring, determining characteristics. | EVOLUTION: The process by which different kinds of living organisms are thought to have developed and diversified from earlier forms during the history of the earth.

What's Next

What to Learn Next

Next, you can explore 'Intrasexual Selection' to understand how competition among individuals of the same sex also drives evolution. Learning about both types of sexual selection will give you a complete picture of how organisms develop amazing and diverse traits!