18.2Variation and Selection
Adaptive features — Cambridge IGCSE Biology 0610 Revision Notes & Topical Questions
5 min read 15 parts Lesson 2 of 3 1 quiz
Lesson summary
18.2 Adaptive features — IGCSE BIOLOGY notes: Define adaptive features and describe the adaptations of animals, hydrophytes and xerophytes.Adaptive feature = an inherited feature that helps an organism to survive and reproduce in its environment.Fitness — organisms with adaptive …
- Identification
- Desert animals
- Large air spaces in leaves
- Small roots
- Thick waxy cuticle
- Sunken stomata
Section 1 of 15Adaptive features
Adaptive features
Adaptive feature
Adaptive feature an inherited feature that helps an organism to survive and reproduce in its environment.
Fitness
- Fitness organisms with adaptive features are more likely to survive and pass on their alleles.
Identification
- Identification adaptations can be described from images or data, for example a fennec fox with large ears, pale fur and furry feet.
Section 2 of 15Interpreting data on adaptation
Desert animals
- Desert animals a gerbil makes urine much more concentrated than humans, beavers or dolphins.
Benefit
- Benefit it loses little water when excreting urea, which conserves water where it is hard to replace.
Method
- Method compare the feature with other species and link it to the environment.
Section 3 of 15Adaptations of hydrophytes
1Hydrophyte
Hydrophyte a plant adapted to live in extremely wet conditions, such as ponds.
2Large air spaces in leaves
- Large air spaces in leaves give flotation and keep leaves near the surface where there is more light.
3Small roots
- Small roots nutrients can be absorbed from the surrounding water through the tissues.
4Stomata
- Stomata usually open all the time and mainly on the upper epidermis, for easy gas exchange with air.
Section 4 of 15Adaptations of xerophytes
Adaptations of xerophytes
Xerophyte
Xerophyte a plant adapted to live in extremely dry conditions, such as deserts.
Thick waxy cuticle
- Thick waxy cuticle acts as a barrier to evaporation and its shiny surface reflects heat.
Sunken stomata
- Sunken stomata moist air trapped in pits lengthens the diffusion pathway and reduces evaporation.
Rolled leaf with hairs
- Rolled leaf with hairs traps moist air and stops air movement across the stomata, reducing transpiration.
Small needle-shaped leaves
- Small needle-shaped leaves reduce the evaporating surface area.
Roots
- Roots extensive and shallow to absorb rain quickly, or deep to reach water tables.
Thickened leaves or stems
- Thickened leaves or stems contain cells that store water.
Section 5 of 15Hydrophytes and xerophytes compared
| Feature | Hydrophyte | Xerophyte |
|---|---|---|
| Habitat | Very wet | Very dry |
| Leaves | Large, floating, air spaces | Small, rolled or thick |
| Stomata | Open, on upper surface | Sunken in pits |
| Roots | Small | Extensive shallow or deep |
| Main problem | Light and gas exchange | Water loss |
Section 6 of 15More from the specification
1
Adaptive alleles and genetic variation
- Adaptive alleles and genetic variation advantageous mutations in functional genes cause physiological adaptations that provide a means to survive harsh environments.
2
Definition of an Adaptive Feature
- An adaptive feature is an inherited structural, physiological,
- or behavioural characteristic that enhances an organism's survival probability and reproductive fitness in its natural habitat.
3
Xerophytic Adaptations in Desert Flora
- Xerophytes exhibit sunken stomata, thick waxy cuticles, curled leaves,
- and extensive root networks to retard transpiration and withstand prolonged subterranean moisture deficits.
4
Hydrophytic Adaptations in Aquatic Plants
- Hydrophytes possess abundant internal aerenchyma tissue for buoyancy and internal gas diffusion, poorly developed xylem vessels,
- and stomata restricted exclusively to the upper leaf epidermis.
5
Development
- The changes as an organism becomes more complex and mature.
6
Natural selection
- Survival and reproduction of the best-adapted individuals.
7
Selective breeding
- Humans choosing which individuals breed.
8
Phenotypic variation
- Differences in phenotype between organisms of the same species.
9
Artificial selection
- Selective breeding of organisms with desirable traits by humans.
10
Continuous variation
- A range of phenotypes between two extremes.
11
Discontinuous variation
- A limited number of distinct phenotypes with no intermediates.
12
Blood group
- A phenotype set by alleles I-A, I-B and I-O.
13
Variation
- Differences between individuals of the same species.
14
Mutation
- A random change in genetic material.
Section 7 of 15Types of adaptive feature
| Type | Meaning | Example |
|---|---|---|
| Structural | Body shape or form | Webbed feet of a duck |
| Behavioural | Actions | Migration of birds, hibernation of bears |
| Physiological | Internal processes | Concentrated urine in camels |
- Adaptive feature an inherited functional feature that increases chance of survival and reproduction.
Section 8 of 15Examples from different environments
| Organism | Habitat | Adaptation and benefit |
|---|---|---|
| Camel | Desert | Fat store in hump, wide feet to avoid sinking, concentrated urine, long eyelashes against sand |
| Cactus | Desert | Spines reduce water loss, thick stem stores water, shallow widespread roots |
| Polar bear | Arctic | Thick fur and fat for insulation, white colour for camouflage, small ears reduce heat loss |
| Marram grass | Sand dunes | Rolled leaves and sunken stomata reduce water loss |
| Fish | Water | Streamlined shape, gills for oxygen, fins for steering |
| Water lily | Pond | Large floating leaves, air spaces for buoyancy |
Section 9 of 15Predators and prey
Predators
- Predators forward-facing eyes to judge distance, sharp teeth and claws, speed.
Prey
- Prey eyes on the sides for wide vision, camouflage, warning colours, speed.
Behavioural
- Behavioural migration, hibernation and living in groups.
Camouflage
- Camouflage helps avoid being seen by predators or prey, as in a stick insect or arctic hare.
Section 10 of 15Body size and heat
Cold habitats
- Cold habitats insulation and a small surface area to volume ratio reduce heat loss.
Large animals
- Large animals such as a polar bear lose less heat per unit mass than small ones.
Dry habitats
- Dry habitats reduced water loss and increased water storage.
Section 11 of 15How adaptations arise
1
Variation exists in a population.
2
Individuals with helpful features survive and reproduce more.
3
Their alleles pass to the next generation.
4
Over time the feature becomes common.
Section 12 of 15Examples of change by selection
Peppered moth
- Peppered moth pale moths were camouflaged on lichen-covered trees.
- When soot darkened the trees, dark moths were less visible to birds, survived more and became common.
- When air became cleaner, pale moths increased again.
Antibiotic resistance
- Antibiotic resistance a random mutation gives a resistant bacterium that survives treatment and reproduces.
Selective breeding
- Selective breeding similar, but humans choose which individuals breed.
Section 13 of 15More from the specification
1
Morphological adaptation as a survival means
- Morphological adaptation as a survival means thick subcutaneous blubber and dense fur provide an essential physiological means for endothermic animals to endure polar freezing.
2
Adaptive Features and Survival
- An adaptive feature is an inherited functional, structural,
- or behavioural characteristic of an organism that increases its fitness and chance of survival in its natural environment.
3
Natural Selection and Evolution
- In natural selection, environmental selection pressures favor individuals with advantageous genetic variations,
- allowing them to survive, reproduce,
- and pass their beneficial alleles to offspring.
4
Genetic vs Environmental Variation
- Phenotypic variation within a biological species is caused by differences in genes and the influence of external environmental conditions.
- (genetic variation)
5
Xerophytic and Desert Adaptations
- Desert animals like gerbils possess physiological adaptations such as elongated loops of Henle that produce highly concentrated urine, minimizing water loss in arid environments.
6
Natural selection
- Survival and reproduction of the best-adapted individuals.
7
Genetic variation
- Differences in alleles within a population.
8
Phenotypic variation
- Differences in phenotype between organisms of the same species.
9
Artificial selection
- Selective breeding of organisms with desirable traits by humans.
10
Continuous variation
- A range of phenotypes between two extremes.
11
Discontinuous variation
- A limited number of distinct phenotypes with no intermediates.
12
Blood group
- A phenotype set by alleles I-A, I-B and I-O.
13
Species
- A group of organisms that can reproduce to produce fertile offspring.
14
Development
- The changes as an organism becomes more complex and mature.
Section 14 of 15Key terms
| Term | Meaning |
|---|---|
| Adaptive feature | An inherited feature that helps an organism survive and reproduce. |
| Hydrophyte | A plant adapted to very wet conditions. |
| Xerophyte | A plant adapted to very dry conditions. |
| Cuticle | A waxy layer on the leaf surface. |
| Transpiration | Loss of water vapour from leaves. |
| Stomata | Pores in the leaf for gas exchange. |
| Term | Meaning |
|---|---|
| Adaptive feature | An inherited feature that increases survival and reproduction. |
| Structural adaptation | An adaptation of body form. |
| Behavioural adaptation | An adaptation of actions. |
| Physiological adaptation | An adaptation of internal processes. |
| Camouflage | Colouring that hides an organism. |
| Predator | An animal that hunts and eats other animals. |
Section 15 of 15Exam technique
1
Saying adaptations are acquired during life — adaptive features are inherited.
2
Saying individuals change to suit the environment — populations adapt over generations.
3
Giving a feature without its function — state how it helps survival.
4
Saying xerophytes have large leaves — they usually have small or rolled leaves.
1
Saying animals adapt during their lives — adaptations are inherited and arise over generations.
2
Naming a feature without its benefit — state the feature and how it helps the organism.
3
Saying the polar bear is white to be warm — white gives camouflage; fur and fat insulate.
4
Saying behaviour cannot be an adaptation — migration and hibernation are behavioural adaptations.
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