B4.1Theme B — Form and function
Adaptation to environment — IB Biology SL Revision Notes & Topical Questions
5 min read 12 parts Lesson 9 of 13 2 quizzes
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Lesson summary
B4.1 Adaptation to environment — IB BIOLOGY SL notes: Explain how abiotic factors limit species distribution and how organisms and biomes are adapted to their environments.Habitat = the place where an organism livesMany species in a habitat form a community.A habitat is described…
- Sand dune conditions
- Marram grass
- Mangrove conditions
- Aerial roots
- Salt exclusion
- Salt excretion
Part 1 of 10Habitats and abiotic factors
Habitat
Habitat the place where an organism lives
- Many species in a habitat form a community.
- A habitat is described by its geographical location, such as polar, or by its ecosystem type, such as grassland.
Adaptation
- Adaptation a heritable feature that arises by natural selection
- It can be structural, physiological or behavioural.
- Organisms fit their abiotic environment and not just their biotic one.
Abiotic factors
Abiotic factors the non-living factors that affect organisms in a habitat
- Light intensity and wavelength, temperature, water turbidity, humidity, pH, salinity and soil composition.
- Oxygen and carbon dioxide concentration, and wind speed.
| Abiotic factor | Effect on organisms |
|---|---|
| Light intensity | Plants need light for photosynthesis |
| Temperature | Affects the rate of enzyme-controlled reactions |
| Water availability | All organisms need water |
| Soil pH and minerals | Different plants need different pH and nutrient levels |
| Wind speed | Raises water loss from leaves by evaporation |
| Carbon dioxide | Needed by plants for photosynthesis |
| Oxygen | Needed for aerobic respiration |
Part 2 of 10Sand dunes and marram grass
Sand dune conditions
- Sand dune conditions low water, high salinity, low nutrients, dry mobile sand and salty spray
Marram grass
- Marram grass a xerophyte adapted to dry conditions
- Dry air gives a steep water vapour gradient out of the leaf.
- Rolled leaves reduce exposure to wind and trap humid air.
- Stomata are sunken in pits to trap water vapour.
- Inner leaf hairs trap water vapour.
- A thick cuticle and long roots reduce loss and reach deep water.
- Higher humidity around the leaf reduces the gradient and so the evaporation.
Part 3 of 10Mangrove swamps
Mangrove conditions
- Mangrove conditions tropical coastal habitats often submerged in sea water
- They have high salinity, low fresh water and low oxygen in waterlogged mud.
Challenges
- Submerged root cells cannot take in oxygen.
- Sea water has a higher solute concentration than the root cells, so water could be lost by osmosis.
Aerial roots
- Aerial roots the parts above water take in oxygen and give stability in soft mud
- Black mangroves have pneumatophores that grow upward out of the mud.
- Prop roots are partly underwater and shelter marine animals.
Salt exclusion
- Salt exclusion red mangroves have root cells that block salt from entering the water-transport system
Salt excretion
- Salt excretion black mangroves take in salt water and excrete excess salt through salt glands in the leaves
Part 4 of 10Range of tolerance and limiting factors
Range of tolerance
Range of tolerance the range of conditions a species can survive, around an optimum
- Mangrove grows best at 3-27 ppt salinity but survives up to about 75 ppt.
- Beyond the critical minimum or maximum the population falls to zero.
Limiting factor
Limiting factor any biotic or abiotic factor that restricts the growth of organisms
- Distribution is limited by the least favourable factor.
- Abiotic factors interact to decide the distribution of a species.
Extreme specialists
- Extreme specialists they have a wide tolerance or an optimum shifted from average
- They thrive where competition is low.
- They do less well in moderate habitats because of competition.
Part 5 of 10Investigating distribution with transects
Sampling
- Sampling measuring a small area to represent a large one, which saves time and needs a sample large enough to be representative
Transect
- Transect a line laid across a site to measure abundance along an environmental gradient
- Continuous line transectevery species touching the tape is recorded.
- Interrupted line transectspecies touching the line at regular intervals are recorded.
- Continuous belt transectquadrats are placed end to end.
- Interrupted belt transectquadrats are placed at regular intervals.
1
Lay a tape from the shore to the inland dune.
2
Place quadrats at regular intervals.
3
Record species cover in each quadrat.
4
Measure the relevant abiotic factors at each point.
5
Plot the species and the factors against distance.
6
Look for correlations using a test such as Spearman's rank or chi-squared, remembering correlation does not prove cause.
- Kite diagram
- shows distribution by position along a line and abundance by the width of the kite
- Abiotic data are added in sections beneath.
Part 6 of 10Measuring abiotic factors
| Abiotic factor | Method |
|---|---|
| Air temperature | Thermometer |
| Rainfall | Rain gauge |
| Humidity | Hydrometer or electronic sensor |
| Dissolved oxygen | Electronic oxygen sensor |
| Water turbidity | Turbidity meter or a Secchi disc |
| Light intensity | Electronic light meter |
| Landscape relief | Contour lines on a map or GPS |
| Site aspect | Compass |
| Slope incline | Clinometer |
| Soil or water pH | Indicator solution |
| Soil water content | Mass of a soil sample before and after drying |
- Relevance
- measure only the abiotic factors relevant to the study, using sensors where possible
Part 7 of 10Coral reefs
Coral
- Coral a symbiosis between a coral polyp and zooxanthellae algae
- The polyp gives shelter and the algae photosynthesise to make carbon compounds.
- Some polyps secrete calcium carbonate, which builds up to form a reef.
Distribution
- Distribution reef-building corals live only in the tropics and subtropics, mainly between 30° N and 30° S
- Corals have a narrow range of tolerance for every factor below.
| Factor | Effect on reef formation |
|---|---|
| Water depth | Shallow, so light reaches the algae |
| pH | H+ ions combine with carbonate ions, so skeletons form slowly or dissolve |
| Salinity | About 32-42 ppt, and freshwater run-off reduces it |
| Water clarity | Sediment and pollution reduce light |
| Temperature | About 20-28 °C and best above 23 °C |
Bleaching
- Bleaching high temperatures make polyps expel their algae
Ocean acidification
- Ocean acidification carbon dioxide from fossil fuels dissolves in the sea and lowers the pH, reducing coral growth
Part 8 of 10Biomes and climographs
Biome
Biome a large community of plants and animals that develops as a result of environmental factors
- It is named after its dominant vegetation.
- Temperature and rainfall largely decide which biome develops.
- Rainforests have the highest biodiversity of the terrestrial biomes.
Climograph
- Climograph plots mean annual rainfall against temperature
- (Whittaker's diagram)
- 200 cm and 25 °C gives tropical seasonal forest.
- 300 cm and 15 °C gives temperate rainforest.
- 100 cm and 0 °C gives taiga.
1
Read the temperature axis and line.
2
Read the rainfall axis and bars.
3
Find the months of highest and lowest values.
4
Work out the annual range of temperature.
5
Estimate the total annual rainfall.
6
Match the pattern to a biome.
- Cautions
- boundaries are gradual transitions, soil type and grazing also matter, and the axes may be swapped
Part 9 of 10Major biomes
| Biome | Annual rainfall | Temperature | Community |
|---|---|---|---|
| Tropical forest | 2000-10 000 mm | 20-25 °C | Layered, highly productive, very high biodiversity, nutrient-poor soil |
| Temperate forest | 750-1500 mm | Seasonal, no extremes | Deciduous trees, fertile soil, high biodiversity |
| Taiga | 300-900 mm, much snow | -40 to 20 °C | Conifers, low productivity |
| Grassland | 500-950 mm | -20 to 30 °C | Grasses, grazing animals, low productivity |
| Tundra | 150-250 mm | -50 to 18 °C | Mosses, lichens, migrating animals |
| Hot desert | Under 250 mm | Hot days, cold nights | Sparse, very low productivity |
- Convergent evolution
- similar climates on different continents give similar communities of unrelated species
- South American cacti and African euphorbias both have spines and succulent stems.
Part 10 of 10Named adaptations
Saguaro cactus
- Saguaro cactus waxy stem, spines, expanding water-storage tissue, and a deep taproot plus shallow surface roots
Desert plants
- Desert plants small or no leaves and CAM photosynthesis
Kangaroo rat
- Kangaroo rat burrows by day, gets water from food and makes very concentrated urine
Fennec fox
- Fennec fox large ears for heat loss and nocturnal habits
Kapok tree
- Kapok tree grows rapidly to the canopy for light and has buttress roots
Rainforest plants
- Rainforest plants drip tips, climbing lianas, and epiphytes that grow on branches to reach light
Orchid mantis
- Orchid mantis the female mimics a flower to catch pollinators
Key terms
| Term | Meaning |
|---|---|
| Habitat | The place where an organism lives. |
| Abiotic factor | A non-living factor, such as temperature or salinity, that affects organisms. |
| Limiting factor | Any biotic or abiotic factor that restricts the growth of organisms. |
| Range of tolerance | The range of conditions within which a species can survive. |
| Transect | A line laid across a site to measure how abundance changes along a gradient. |
| Biome | A large community of plants and animals developed as a result of environmental factors. |
| Climograph | A graph of mean annual rainfall against temperature used to predict the biome. |
| Xerophyte | A plant adapted to dry conditions. |
Avoid these mistakes
1
Saying adaptations appear because the organism needs them — they arise by natural selection of heritable variation
2
Saying a species survives anywhere with its optimum — it also needs conditions within the range of tolerance for every factor
3
Saying correlation along a transect proves that the abiotic factor is the cause — other factors may also vary
4
Saying biomes are separated by sharp boundaries — they shift gradually
Marked practiceQuizzes for this lesson
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