B4.1 Adaptation to environment

Guiding questions

How do a species' adaptations relate to its habitat?
Why do ecosystems in the same land biome resemble each other?

Slides

1 of 18

Notes

Written for this site from the class slides, with textbook page references for each statement. The chapter is on pages 341–362 of the course textbook. Image credits are on slide 18.

Habitats and adaptations

B4.1.1

Habitat

pp. 341–342

A habitat is the place where an organism, population, species or community lives. A description can include geographical and physical location, and the type of ecosystem.

B4.1.2

Adaptations to the abiotic environment

pp. 342–344

Plant	Challenges	Adaptations
Marram grass, sand dunes	Little water, salt spray, wind	Rolled leaves, sunken stomata, thick cuticle, deep roots and rhizomes
Mangrove trees, swamps	Anaerobic, salty, soft mud	Pneumatophores, stilt roots, salt glands

B4.1.3

Abiotic variables and distribution

pp. 344–345

Plants are affected by temperature, water, light, soil pH, salinity and mineral nutrients. Animals are affected by temperature, water and breeding sites, among others. A species' adaptations give it a range of tolerance.

B4.1.4

Range of tolerance

pp. 345–352

Each species thrives in an optimum range, is under stress towards the limits, and cannot survive beyond them. A transect lets you correlate the distribution of a species with an abiotic variable, using data you collect yourself. A correlation alone does not prove cause.

Reefs and biomes

B4.1.5

Conditions for coral reefs

p. 353

Slide: a table of the conditions coral reefs need

Reefs need shallow, clear, warm water with suitable pH and salinity. Most reef-building corals live less than 25 m deep, at about 23–29 °C. Corals have a mutualistic relationship with algae, the zooxanthellae, which need light.

B4.1.6

Climate determines land biomes

pp. 354–355

For any given temperature and rainfall pattern, one type of natural ecosystem is likely to develop. A graph of these two variables shows where each biome is found.

B4.1.7

Similar communities in each biome

pp. 356–359

Similar abiotic conditions produce similar selection pressures, and so convergent evolution gives similar communities. Know the climates of tropical forest, temperate forest, taiga, grassland, tundra and hot desert.

B4.1.8

Hot deserts and tropical rainforests

pp. 359–361

Species	Biome	Adaptations
Saguaro cactus	Hot desert	Water-storing stem, spines, shallow wide roots
Fennec fox	Hot desert	Large ears lose heat, active at night
Spider monkey	Rainforest	Long limbs and a gripping tail
Poison dart frog	Rainforest	Toxins and warning colours

Videos

Select a video to play it here. Select it again to close it.

How Do Corals Build Reefs?California Academy of SciencesB4.1.5

Note-taking sheet

Print this guide and complete it as you work through the slides and videos. It asks for your own explanations, so close the notes while you try each section.

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Practice questions

A printable worksheet covering all eight statements, from quick recall to data questions and a longer answer. It has 40 marks and takes about 40 minutes, or you can do one section at a time.

Worksheet PDF

Your teacher has the mark scheme.

Data-based questions

Data questions PDF

Questions built on realistic experimental data, in the style of Paper 1B and Paper 2. Work them on paper and show your working. 12 marks in total. Your teacher has the mark scheme.

Warming and nutrients in the tundra

6 marks

Plots of Arctic tundra were given one of four treatments for ten years: none (control), warming with small clear greenhouses, added fertiliser (nitrogen and phosphorus), or both. The graph shows the mean biomass of three groups of plants at the end.

Bar chart of biomass. Control: shrubs 120, grasses 40, mosses 90. Warmed: 150, 45, 70. Fertilised: 260, 90, 40. Both: 330, 95, 25 grams per square metre.

Calculate the total biomass of the three groups in the control plots. [1]
Calculate the percentage change in shrub biomass in plots that were warmed and fertilised, compared with the control. [1]
Compare the effects of the treatments on shrubs and mosses. [2]
Suggest reasons for the changes in moss biomass. [2]

Plants that grow on trees

6 marks

Epiphytes on a tree branch — Image: James St. John, CC BY 2.0, Wikimedia Commons.

Epiphytes, such as mosses, ferns and orchids, grow on the branches of trees and take water from rain and mist. The percentage of branch surface covered by epiphytes was measured in a lowland rainforest and a mountain cloud forest, on branches at three angles.

Bar chart of epiphyte cover. Horizontal branches: lowland 35%, cloud forest 85%. Sloping: 20% and 60%. Vertical: 5% and 25%.

State the epiphyte cover of horizontal branches in the cloud forest. [1]
Compare epiphyte cover in the two forests. [2]
Suggest two reasons why there are more epiphytes in the cloud forest. [2]
Suggest why horizontal branches have the most epiphytes. [1]

Practical

Abiotic factors along a transect

Field50 minB4.1.3

You will need: Tape measure, light meter or phone app, thermometer, quadrat

Run a tape from open ground into shade
Measure light and temperature every two metres
Record which plants are present at each point
Plot the results and describe any link between distribution and conditions

Safety: Check the site first. Watch for trip hazards and stinging plants.

Carry this out with your teacher's supervision and follow your school's lab rules.

Nature of science and TOK

Nature of science

Patterns and trends

Mapping climate against vegetation reveals biome patterns that help to explain where organisms live.

Theory of knowledge

Are categories discovered or invented?

Nature has no sharp borders between biomes. Consider whether our categories describe nature or simply help us to think about it.

Syllabus statements

Summarised in our own words. Use each code to find the exact wording in your textbook or the IB subject guide.

B4.1.1What a habitat is: where a community, species, population or organism livesp. 341
B4.1.2How organisms are adapted to the non-living conditions of their habitatp. 342
B4.1.3Non-living factors that affect where species are foundp. 344
B4.1.4How far an organism can tolerate a limiting factorp. 349
B4.1.5The conditions needed for coral reefs to formp. 353
B4.1.6How non-living factors decide where land biomes occurp. 354
B4.1.7Biomes: ecosystems with similar communities, because of similar conditions and convergent evolutionp. 356
B4.1.8How organisms are adapted to hot deserts and tropical rainforestsp. 359

HL extension

B4.1 has no HL-only content. SL and HL students learn the same material here.