18. Variation and Selection (Part 1) (Cambridge IGCSE Biology 0610 for exams in 2023, 2024 and 2025)

Summary

This video offers a comprehensive overview of Chapter 18, Variation and Selection, from the Cambridge IGCSE Biology syllabus. It explains key concepts such as genetic and phenotypic variation, continuous and discontinuous variation, and the causes behind these differences, including mutation and environmental factors. The video also covers adaptive features in organisms, with examples from hydrophytes and xerophytes, highlighting how they are specially adapted to survive in their respective environments. This educational content provides clear insights into the role of variation and selection in biology.

Takeaways

• 😀 Variation refers to the differences between individuals of the same species, and it can be genetic and/or phenotypic.
• 😀 Genetic variation occurs due to differences in the genetics of individuals within a species, including traits like blood group, eye color, gender, and tongue-rolling ability.
• 😀 Phenotypic variation is caused by differences in observable features and can be influenced by genetics or the environment.
• 😀 Environmental factors such as climate, diet, and lifestyle can lead to phenotypic variation, like differences in body type between active and inactive individuals.
• 😀 Genetic variation in populations arises from mutation, meiosis, random mating, and random fertilization.
• 😀 Continuous variation leads to a range of phenotypes between two extremes, such as body length and mass, and is influenced by both genes and the environment.
• 😀 Discontinuous variation results in distinct, non-overlapping phenotypes, like blood groups and seed shape/seed color in peas, and is usually controlled by genes.
• 😀 Mutation is a random change in the base sequence of DNA and can occur due to factors like ionizing radiation or exposure to certain chemicals.
• 😀 Mutations can lead to the formation of new alleles, which may change an organism's traits, improving survival chances, such as in the case of rabbits with lighter fur to blend into their environment.
• 😀 Adaptive features are inherited traits that help an organism survive and reproduce in its environment, such as those seen in hydrophytes and xerophytes.
• 😀 Hydrophytes, plants adapted to water environments, have wide flat leaves, small roots, and stomata on the upper leaf surface for efficient gas exchange.
• 😀 Xerophytes, plants adapted to dry environments, have thick cuticles, small leaves, deep roots, and water-storing structures to minimize water loss and maximize uptake.

Q & A

What is variation in biology?

Variation refers to the differences between individuals of the same species. It can be genetic, phenotypic, or a combination of both.

What is genetic variation?

Genetic variation is the differences in genetics among individuals within the same species, such as differences in blood group, eye color, gender, and the ability to roll the tongue.

What is phenotypic variation?

Phenotypic variation is the variability of observable features (phenotypes) within a population. It can be caused by genetics or environmental factors like climate, diet, and lifestyle.

How can environmental factors cause phenotypic variation?

Environmental factors such as climate, diet, and lifestyle can influence observable traits. For example, an active person may develop a more muscular physique compared to someone with a less active lifestyle.

What are the causes of genetic variation in populations?

Genetic variation in populations can be caused by mutations, meiosis, random mating, and random fertilization.

What is continuous variation?

Continuous variation is when a trait has a range of possible values with no distinct categories. Examples include body length and mass, where there are no clear-cut groups, just a spectrum of possibilities.

What is discontinuous variation?

Discontinuous variation results in distinct categories with no intermediates. Examples include blood groups and seed shape, where traits fall into clear, separate groups.

What is a mutation in genetics?

Mutation is a random change in the base sequence of DNA, which can be caused by factors such as ionizing radiation (X-rays, gamma rays) or exposure to certain chemicals (e.g., tar in tobacco).

How can a mutation be beneficial to a population?

A mutation can introduce a new allele that provides an advantage, such as improved camouflage. For example, a mutation leading to lighter-colored fur in rabbits could help them blend into their environment and avoid predators.

What are adaptive features in organisms?

Adaptive features are inherited characteristics that help organisms survive and reproduce in their environment. For instance, hydrophytes (water plants) have features like wide leaves for better light absorption, while xerophytes (dry environment plants) have features like thick waxy leaves to minimize water loss.