10A: Adaptations
10A: Adaptations
1. Key definitions
Habitat: the place where an organism lives.
Environment: the surroundings and conditions that affect an organism.
Adaptation: an inherited characteristic that helps an organism survive and reproduce in its environment.
Evolution: changes in inherited characteristics within a population over generations.
Natural selection: organisms with helpful inherited characteristics are more likely to survive and reproduce, passing those characteristics to their offspring.
2. Three types of adaptations
Type | Meaning | Examples |
Structural | Physical features of an organism | Thick fur, claws, large ears |
Behavioural | Actions an organism performs | Migration, huddling, being nocturnal |
Physiological | Internal processes of the body | Concentrated urine, temperature regulation |
Memory trick:
Structural = body structure.
Behavioural = behaviour.
Physiological = body functions.
3. Natural selection
Learn these five steps:
Individuals in a population have inherited variations.
The environment creates challenges, such as heat or limited water.
Individuals with helpful adaptations are more likely to survive.
These individuals reproduce and pass on their genes.
Over many generations, helpful characteristics become more common in the population.
4. Adaptations to desert environments
Deserts have very low rainfall, limited water, little shade and extreme temperature changes. Days can be very hot, while nights can become extremely cold.
Desert animals
Adaptation | How it helps |
Large, thin ears | Increase heat loss |
Flat feet in camels | Spread body weight over sand |
Long eyelashes | Protect eyes from blowing sand |
Narrow nostrils | Reduce sand entering the nose |
Nocturnal behaviour | Avoids the hottest part of the day |
Burrowing | Provides shelter from extreme temperatures |
Concentrated urine | Reduces water loss |
Dry faeces | Reduce water loss by reabsorbing water in the intestine |
Thorny devil's body grooves | Help direct water towards the mouth |
Pale fur | Reflects sunlight and may provide camouflage |
Desert plants
Adaptation | How it helps |
Thick, fleshy stems | Store water |
Spines instead of leaves | Reduce water loss |
Waxy leaf coating | Reduces evaporation |
Widespread roots | Collect water over a large area |
Dropping leaves during dry periods | Reduces water loss |
Green stems | Allow photosynthesis when leaves are absent |
5. Surface area to volume ratio (SA:V)
High SA:V: heat is exchanged more quickly with the surroundings.
Low SA:V: heat is exchanged more slowly, helping an organism retain heat.
Generally, organisms in hot environments may benefit from a higher SA:V to lose heat, while organisms in cold environments benefit from a lower SA:V to conserve heat.
Remember that other adaptations also influence how well an organism survives.
10B: Adaptations to Cold
1. Challenges of cold environments
Cold environments create several challenges:
Low temperatures slow down chemical reactions in cells.
Ice can damage cells and tissues.
Strong winds increase heat loss and can damage plants.
Low nutrient availability limits growth.
Frozen water and snow reduce the availability of liquid water.
2. Structural adaptations
Adaptation | How it helps |
Thick fur | Traps insulating air and reduces heat loss |
Feathers | Trap air and provide insulation |
Fat beneath the skin | Insulates the body |
Compact or rounded body shape | Reduces surface area relative to volume and helps retain heat |
3. Endotherms and ectotherms
Endotherms: mainly mammals and birds; use internal metabolic processes to help maintain body temperature.
Ectotherms: such as snakes and lizards; rely more on external heat sources to regulate body temperature.
4. Torpor, hibernation and brumation
Term | Meaning |
Torpor | A state of reduced metabolic activity that conserves energy |
Hibernation | Prolonged torpor in endotherms during cold conditions |
Brumation | Prolonged torpor in ectotherms during cold conditions |
Example: Mountain pygmy possums can spend up to seven months a year in torpor. They shelter beneath insulating snow, reduce their metabolic rate and allow their body temperature to fall. They become active again in spring to feed and breed.
5. Physiological adaptations to cold
Vasoconstriction
Blood vessels near the skin narrow, reducing blood flow to the body surface. This reduces heat loss to the environment.
Counter-current heat exchange
Warm blood travelling towards the extremities transfers heat to cooler blood returning to the body. This helps keep the body's core warm and reduces heat loss through areas such as the feet, wings and bills of penguins.
6. Behavioural adaptations to cold
Huddling: reduces the amount of body surface exposed to cold air.
Curling up: reduces exposed surface area.
Seeking shelter: protects organisms from cold winds.
Migration: allows animals to move to warmer environments.
7. Plant adaptations to cold
Cold temperatures can slow chemical reactions, while ice crystals can damage cell membranes and block transport tissues.
Plants can survive cold conditions through:
Changing the composition of cell membranes so they function at low temperatures.
Increasing solute concentrations, such as glucose, which can improve freezing resistance.
Producing antifreeze proteins that interfere with ice crystal formation.
Dropping leaves during winter to reduce damage and conserve resources.
Keeping seeds dormant until conditions are suitable for germination.
Deciduous trees
Deciduous trees drop their leaves during certain seasons. This helps them avoid damage to leaves in freezing conditions, conserve water and energy, and reduce the risk of branches breaking under snow or strong winds.
Seed dormancy
Seed dormancy prevents seeds from germinating when conditions are unsuitable. Seeds can remain dormant through winter and germinate when temperature and light conditions improve.
Tree line
The tree line is the boundary beyond which trees cannot grow. It can occur at high elevations or latitudes, where low temperatures are a major limiting factor. Wind, precipitation and nutrient availability can also affect tree growth.
10C: Interdependencies of Species
1. Key ecology definitions
Ecology: the study of how organisms interact with each other and their environment.
Biotic factors: living parts of an environment.
Abiotic factors: non-living parts of an environment, such as temperature, water, sunlight and soil.
Population: individuals of the same species living in the same geographical region.
Community: populations of different species interacting in the same region.
Ecosystem: a community of organisms interacting with each other and the physical environment.
Habitat: the place where an organism lives.
Niche: the role of a species and how it uses its environment.
2. Levels of organisation
Learn these in order from smallest to largest:
Cell: the basic unit of life.
Organism: an individual living thing.
Population: individuals of the same species in one area.
Community: different populations living and interacting in one area.
Ecosystem: communities interacting with the physical environment.
3. Population characteristics
Term | Meaning |
Population size | Total number of individuals |
Population density | Number of individuals per unit area |
Population distribution | The geographical area where a population is found |
Carrying capacity | The maximum population an environment can sustainably support |
Changes in population size
The formula is:
\[ N_{i+1}=N_i+B-D+I-E \]
\(N_i\) = initial population size
\(B\) = births
\(D\) = deaths
\(I\) = immigration, individuals entering
\(E\) = emigration, individuals leaving
Births and immigration increase population size. Deaths and emigration decrease it.
Density-dependent and density-independent factors
Density-dependent factors: their effects depend on population density. For example, competition for limited food becomes stronger when more individuals share the same area.
Density-independent factors: affect populations regardless of their density.
4. Interactions between species
This is one of the most important sections to memorise for your quiz.
The symbols mean:
\(+\) = benefits the organism.
\(-\) = harms the organism.
\(0\) = neither benefits nor harms the organism.
Interaction | Effect | Meaning | Example |
Mutualism | +/+ | Both species benefit | Bees and flowering plants |
Commensalism | +/0 | One benefits, the other is unaffected | Barnacles on whales |
Parasitism | +/- | Parasite benefits, host is harmed | A parasite living on or inside a host |
Predation | +/- | Predator kills and eats prey | A wolf hunting prey |
Competition | -/- | Both are negatively affected by competing for limited resources | Plants competing for sunlight |
Amensalism | -/0 | One is harmed, the other is unaffected | One species inhibits another without being affected itself |
Important differences
Interspecific competition: competition between different species.
Intraspecific competition: competition between members of the same species.
Competitive exclusion: one species is eliminated from a community because of competition.
Parasites
Ectoparasites live on the outside of a host.
Endoparasites live inside a host.
Parasitism usually harms the host but does not necessarily kill it.
Symbiosis
Symbiosis is a close association between organisms of different species. Your PowerPoint includes mutualism, commensalism, parasitism, competition, predation and amensalism among species interactions.
5. Keystone species
A keystone species has a major influence on its ecosystem. Its presence helps maintain the ecosystem and affects the survival or numbers of many other organisms.
Example 1: Sea otters
Sea otters eat sea urchins.
Sea urchins eat kelp.
Sea otters help control sea urchin populations.
This allows kelp forests to remain healthier.
Kelp forests provide habitat and resources for many marine organisms.
Without enough sea otters, sea urchin numbers can increase and damage kelp forests.
Example 2: Grizzly bears
Grizzly bears eat salmon that return from the ocean to rivers to reproduce. Bears and partly eaten salmon carcasses help transfer nutrients from the ocean into surrounding forests, supporting the ecosystem.
Final Quiz Checklist
Test your knowledge
0 of 13
Define adaptation, evolution and natural selection.
Explain structural, behavioural and physiological adaptations.
Describe desert animal and plant adaptations.
Explain surface area to volume ratio.
Distinguish endotherms from ectotherms.
Define torpor, hibernation and brumation.
Explain vasoconstriction and counter-current heat exchange.
Describe how plants survive freezing conditions.
Define population size, density, distribution and carrying capacity.
Use the population change formula.
Identify all six species interactions and their symbols.
Distinguish interspecific from intraspecific competition.
Explain what a keystone species does.
Reset checklist