MYP Biology - Variation and Adaptation Notes

4.4 Variation and Adaptation to the Environment

Learning Objectives

  • Define variation and explain the types of variation.

  • Explain causes of variation.

  • Analyze how adaptations help organisms survive in different environments.

Variation

  • Variation refers to the differences between each organism in a species.

  • Variation is beneficial to a species as it allows natural selection to occur and reduces the risk of extinction from disease.

Types of Variation

  • Phenotypic variation:

    • The phenotype of an organism refers to its observable characteristics, such as height or hair color.

    • Phenotypical variation can be caused by both genetic and environmental factors.

    • Example: The potential height of an organism is decided in genes which come from the parents, although some organisms will never reach this height as they do not receive enough nutrients from their environment.

  • Genetic variation:

    • Each organism in a species has a different set of DNA, which is due to genetic variation.

    • Genetic variation is increased during meiosis, which produces gametes.

    • Each gamete has a different set of alleles, which means that when the two gametes fuse an entirely new set of genes are produced.

Continuous vs. Discontinuous Variation

  • Continuous variation:

    • Results in a range of phenotypes between two extremes, for example, height or weight.

  • Discontinuous variation:

    • Is limited to a discrete number of categories, such as blood group, which is limited to A, B, AB, or O in humans.

    • Discontinuous variation is mainly caused by genes alone.

Continuous Variation vs. Discontinuous Variation

  • Continuous Variation

    • Nature of trait: Measurable on a scale

    • Number of traits: Many, with intermediate values

    • Genetic Control: Multiple genes, often with environmental influence

    • Graph Representation: Normal distribution curve or histogram

  • Discontinuous Variation

    • Nature of trait: Categorical, distinct groups

    • Number of traits: Few, with no intermediates

    • Genetic Control: Usually one gene, less environmental influence

    • Graph Representation: Bar graph

Mutation

  • Mutations are genetic changes which result in a change in the sequence of DNA bases.

  • These changes can occur due to a variety of factors, including exposure to some chemicals and ionizing radiation.

  • If the mutation occurs at a particular allele, this allele may be altered, changing how it functions.

  • This is how new alleles are formed.

Think-Pair-Share Questions

  • What do you notice about this animal/plant that might help it survive?

  • Do you think it would survive in a different environment? Why or why not?

  • What would happen if these conditions suddenly changed?

Adaptation

  • Adaptation is a special feature or behavior that helps a living thing survive and do well in its environment.

  • Adaptive features are inherited functional features that help the organism by increasing its fitness, which is the ability of the organism to survive and reproduce in its environment.

Why Adapt?

  • Adaptations allow animals to get the resources they need to survive.

  • Find Food and Water

  • Some animals have adaptations that help them avoid being eaten.

  • Protects from Predators

    • A giraffe’s long neck helps it reach leaves high up in tall trees.

    • A chameleon can change its color to blend in with its surroundings and hide from predators.

  • Adaptations help living things survive in extreme environments like deserts or the Arctic.

  • Survival in Harsh Climates

  • Adaptations can improve the chances of finding mates and raising young.

  • Reproduce Successfully

    • Bright feathers of a male peacock attract female peacocks during mating season.

    • A polar bear has thick fur and a layer of fat to keep it warm in freezing temperatures.

3 Types of Adaptations

  • Structural Adaptations

    • These are physical features of an organism’s body that help it survive or live comfortably in its environment.

  • Behavioral Adaptations

    • These are actions or behaviors that organisms do to help them survive. These behaviors can be learned or instinctive.

  • Physiological Adaptations

    • These are internal body processes or functions that help an organism survive in its environment.

Structural Adaptations Example

  • Ex: Hard Shell of an Armadillo

    • Structural adaptations are physical features of an organism’s body that help it survive, find food, protect itself, or live comfortably in its environment.

    • Purpose: Acts as a tough protective armor against predators.

    • Survival Advantage: When threatened, the armadillo can roll into a ball, using its hard shell to shield its soft, vulnerable parts from danger.

Behavioral Adaptations Example

  • Ex: Hibernation in Bears

    • Behavioral adaptations are behaviors that organisms do to help them survive in their environment. These behaviors can be learned or instinctive.

    • Purpose: Bears go into a deep, sleep-like state during winter, slowing their heart rate and conserving energy.

    • Survival Advantage: Allows bears to survive cold winters when food is scarce.

Physiological Adaptations Example

  • Ex: Toxin in Poison Dart Frogs

    • Physiological adaptations are internal body processes or functions that help an organism survive in its environment.

    • Purpose: Poison dart frogs produce toxic chemicals through their skin, which can be harmful or even deadly to predators.

    • Survival Advantage: The toxins act as a strong defense mechanism.