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Biomes are groups of the ecosystem that have the same climate and dominant communities. They are complex terrestrial (mostly earth's surface)  systems of abiotic and biotic factors that cover a large area and are characterized by certain soil & climate characteristics and by certain groupings of plants and animals. Living organisms prefer certain climatic conditions. This means that animals and plants are usually found only in regions that suit them. A polar bear, for example, will be found in a region of low temperature and low humidity. Such a region of the biosphere is called the arctic.
In this unit, we will look at the different types of biomes and the factors that influence the organisms in those biomes. This unit is a minimum of 4.5 hours

Significant Ideas

  • Climate determines the type of biome in a given area, although individual ecosystems may vary due to many local abiotic and biotic factors.

  • Succession leads to climax communities that may vary due to random events and interactions over time. This leads to a pattern of alternative stable states for a given

  • ecosystem.

  • Ecosystem stability, succession, and biodiversity are intrinsically linked.


Big questions:

  • What strengths and weaknesses of the systems approach and the use of models have been revealed through this topic?

  • How are the issues addressed in this topic of relevance to sustainability or sustainable development?

  • What are the strengths and weaknesses of models of succession and zonation?

  • How could the R/R ration be used to estimate whether the harvesting of natural capital, such as trees, is sustainable or not?


Knowledge & Understanding:

2.4.U1 Biomes are collections of ecosystems sharing similar climatic conditions that can be grouped into five major classes: aquatic, forest, grassland, desert, and tundra. Each of these classes has characteristic limiting factors, productivity, and biodiversity.
[You are encouraged to study at least four contrasting pairs of biomes of interest, such as temperate forests and tropical seasonal forests; or tundras and deserts; or tropical coral reefs and hydrothermal vents; or temperate bogs and tropical mangrove forests]
[You could be given a graph and asked to describe what it shows. Pick out trends]

  • Define biome

  • Distinguish between weather and climate

  • List the five major classes of biomes.

  • Explain the distributions, structure, biodiversity, and relative productivity of four pairs of contrasting biomes.

  • Use case studies to explain the distribution, structure, limiting factors, productivity, and biodiversity of contrasting biomes.


There are two basic categories of communities: terrestrial (land) and aquatic (water). These two basic types of community contain smaller units known as biomes. A biome is a large-scale category containing many communities of a similar nature, whose distribution is largely controlled by climate

Aquatic - which are further subdivided into:

  • Freshwater: ponds and lakes, streams and rivers, and wetlands such as bogs and swamps.

  • Marine: deep ocean, coral reefs, estuaries, and mangrove swamps.

Forest – tropical rainforest, temperate forests and boreal or taiga.
Grassland – savanna and temperate.
Desert – hot, coastal, and cold.
Tundra – arctic and alpine.

A biome has distinctive abiotic factors and species which distinguish it from other biomes. Water, insolation, and temperature are the climates control important when understanding how biomes are structured, how they function, and where they are found around the world. Biomes usually cross national boundaries (biomes do not stop at a border; for example, the Sahara, tundra, tropical rainforests).

Refer to the prevailing climate and limiting factors. For example, tropical rainforests are found close to the equator where there are high insolation and rainfall and where light and temperature are not limiting. The other biome may be, for example, temperate grassland or a local example. Limit climate to temperature, precipitation, and insolation.  It is required that you need to be able to explain the distribution, structure, and relative productivity of tropical rainforests, deserts, tundra, and one other biome. Climate should only be explained in terms of temperature, precipitation, and insolation only.



  • cover 20-30 percent of the land surface

  • dry air

  • high temperatures (45-49 C in the day)

  • low precipitation (250 mm yr-1)

  • low rates of photosynthesis

  • low NPP rates

  • vegetation scarce

  • soil rich in nutrients and can support a plant that can survive there



  • found in high latitudes

  • days are short

  • limit levels of sunlight

  • water may be locked up in ice, limiting water resources

  • photosynthesis and productivity rates are low

  • low temperatures

  • soil may be permanently frozen

  • nutrients in the soil are limited

Tropical rainforest:

  • high temperatures (average 26 C )

  • high rainfall (over 2500 mm yr -1)

  • near the equator

  • high light levels throughout the year

  • all-year-round growing season

  • high levels of photosynthesis

  • high rates of NPP throughout the year

  • high diversity of animals and plants

  • low levels of nutrients in the soil


Temperate forest:

  • seasonal weather (hot summers/cold winters)

  • 2 types of tree types in forests; Evergreen + deciduous could be in one forest or contain both trees

  • rainfall average between 500-1500 mm yr-1

  • productivity lower than rainforest

  • the mild climate, lower average temperature / lower rainfall

Grasslands (tropical and temperate)

  • wet and hot season/dry and warm season

  • November – April: approximately 800 mm rain (hot and wet) 

  • May – October: less than 50 mm rain throughout the dry season.(dry and warm)

  •  the high 30s (°C) but can get up into the high 40s (hot and wet)

  •  the temperature in the low 30s (°C) but can dip into the 20s.(warm and dry)

  • NPP lower than forest biome

  • long dry seasons result in no NPP

  • high diversity of animals

  • Savanna soils are poor and lacking in nutrients and organic matter because of the high rainfall

  • temperate soils higher nutrient level

Aquatics (freshwater, coral reefs deep oceans)

  • water absorbs some light and limits photosynthesis

  • deep oceans have no light for photosynthesis

  • freshwater may freeze in temperate or polar winters

  • NPP high in tropical coral reefs

  • NPP very low in deep oceans

  • NPP moderate in freshwater

  • High biodiversity in coral reefs

  • Low biodiversity in deep oceans

  • Moderate to low biodiversity in freshwater

You should study at least four contrasting pairs of biomes. Examples of contrasting biomes include; temperate forests and tropical seasonal forests; tundra and deserts; tropical coral reefs and hydrothermal vents; temperate bogs and tropical mangrove forests.

Climate Data

Climate Graphs

2.4.U2 Insolation, precipitation, and temperature are the main factors governing the distribution of biomes.

  • ​Explain how insolation, precipitation, and temperature determine the distribution of the biomes

The distribution of biomes results from insolation, precipitation, and temperature.  Climate, terrain (or geography), and ocean and wind currents also play important roles.
Insolation is measured by the amount of solar energy received per square centimeter per minute. As the sun rotates around the sun, the position of the landmasses will change resulting in various concentrations of solar radiation over the landmasses.

The atmosphere and its circulation systems determine where moisture-carrying air masses do and do not go. The energy source of those circulatory systems is the sun. The sun's energy drives atmospheric movements, sustains photosynthesis, and propels the seasons.

The main geographic factors are

  1.  the distribution of the landmasses and ocean basins

  2. the topography of the continents. 

Plant biomes are based primarily on the distribution of the dominant vegetation. 
Animal biomes are usually named after regions because their distribution is more difficult to define.

A biome's boundaries are determined by climate more than any other factor. Eg tundra is colder and has a shorter growing season than other biomes, it has fewer kinds of vegetation. Towards the equator, precipitation becomes increasingly important, producing temperate communities of desert, grassland, and forest in increasing order of precipitation. In the tropical and subtropical biomes which occur in the equatorial latitudes, there is a relatively smaller range of temperature during the year, and their variation is also determined by the amount of precipitation. Thus there are not only tropical forests but also tropical grasslands and tropical deserts. In addition, seasonal distribution is important. Some areas could be a tropical forest but that all their rain comes in just two months rather than evenly distributed

Another important factor is the altitude. Changes in vegetation with increasing altitude resemble changes in vegetation due to increasing latitude. It isn't entirely the same. For example, increasing altitude means increasing UV. And increasing latitude usually means different amounts of light because of changing day length, this doesn't happen in changing altitude

2.4.U3 The tricellular model of atmospheric circulation explains the distribution of precipitation and temperature and how they influence the structure and relative productivity of different terrestrial biomes.
[You will not have to know the names of the cells but you may be asked to explain why the biomes are where they are and why they have the climate they do.]

  • Describe how the tricellular model contributes to the distribution of biomes


​The tricellular model explains the distribution of precipitation and temperature and how they influence the structure and relative productivity of different terrestrial biomes. The tricellular model is made up of three different air masses, these control atmospheric movements and the redistribution of heat energy. The three air masses, starting from the equator, are called the Hadley cell, Ferrel cell, and the polar cell.

The tricellular model also contains the ITCZ (Inter-tropical convergence zone), this is the meeting place of the trade winds from both the northern hemisphere and the southern hemisphere. The ITCZ is a low-pressure area where the trade winds, which have picked up latent heat as they crossed oceans, are now forced to rise by convection currents. These rising convection currents are then cooled adiabatically to form massive cumulonimbus clouds.

  • As substance gain heat energy, density decreases so particles rise

  • As you go up in altitude air cools, becomes denser, and falls back towards the earth’s surface.

  • These convection currents drive the Earth’s wind patterns and affect the biomes.

  • The same phenomena drive ocean currents

2.4.U4 Climate change is altering the distribution of biomes and causing biome shifts.

  • ​Discuss how climate change is impacting biomes and causing them to shift.

 A changing global climate threatens species and ecosystems. The distribution of species is largely determined by climate, as is the distribution of ecosystems and plant vegetation zones (biomes). Climate change may simply shift these distributions, but often, barriers and human presence will provide no opportunity for distributional shifts. For these reasons, some species and ecosystems are likely to be eliminated by climate change.

If significant climate change occurs many natural populations of wild organisms will be unable to exist within their natural ranges. Changes in temperature and precipitation, and resultant changes in vegetation and habitat, are likely to seriously affect the suitability of the locales where species are presently found. Thus, climate change is an additional factor threatening the survival of species

Climate changes are happening very fast, within decades, and organisms change slowly, over many generations through evolutionary adaptation. All they can do to adapt to fast change is to move. They move:

  • towards the poles where it is cooler

  • higher up mountains where it is cooler 

  • towards the equator where it is wetter

In Africa in the Sahel region, woodlands are becoming savannas

2.4.U5 Zonation refers to changes in the community along an environmental gradient due to factors such as changes in altitude, latitude, tidal level, or distance from shore (coverage by water)
[It is important to distinguish zonation (a spacial phenomenon) from succession (a temporal phenomenon)]
​[Named examples of organisms from the pioneer, intermediate and climax communities should be provided]

  • ​Define and give an example of zonation.

​Zonation refers to changes in the community along an environmental gradient due to factors such as changes in altitude, latitude, tidal level, or distance from shore (coverage by water).

The distinct vertical layers experience particular abiotic conditions. This is particularly clear in the distribution of plants and animals on a rocky seashore, where different species inhabit a series of horizontal stripes or belts of the shore, approximately parallel to the water's edge. In many places, the strips (zones) are sharply bounded by the differently colored seaweeds that populate them.

The division of vegetation in relation to a successional sequence (e.g. in sand-dunes), implying that spatial zonation may correspond to temporal processes. 

​Kite diagrams are a chart that shows the number of animals (or percentage cover for plants) against distance along a transect. The distribution of organisms in a habitat is affected by the presence of other living organisms, such as herbivores or predators that might eat them. It is also affected by abiotic factors (physical factors) such as availability of light or water. The width of the “kite” represents the number of species.

The kite diagram is frequently used to show zonation along a transect. A gradual change in the distribution of species across a habitat is called zonation. It can happen because of a gradual change in an abiotic factor. A transect is a line across a habitat or part of a habitat. It can be as simple as a string or rope placed in a line on the ground. The number of organisms of each species can be observed and recorded at regular intervals along the transect.


2.4.U6 Succession is the process of change over time in an ecosystem involving pioneer, intermediate, and climax communities
[It is important to distinguish zonation (a spacial phenomenon) from succession (a temporal phenomenon)]
​[Named examples of organisms from the pioneer, intermediate and climax communities should be provided]
[You must know an example of success with specific species names. You can pick any type of succession - hydrosere, halosere, psammosere, lithosere, or xerosere. Pick one with names that you find easy to remember.​

  • Define and give an example of succession.


​​Succession is a directional non-seasonal cumulative change in the types of plant species that occupy a given area through time. It involves the processes of colonization, establishment, and extinction which act on the participating plant species. Most successions contain a number of stages that can be recognized by the collection of species that dominate at that point in the succession. Succession begins when an area is made partially or completely devoid of vegetation because of a disturbance. Some common mechanisms of disturbance are fires, wind storms, volcanic eruptions, logging, climate change, severe flooding, disease, and pest infestation. Succession stops when species composition changes no longer occur with time, and this community is said to be a climax community.

Examples of succession:

  • Hydrosere: Succession in a body of fresh water. In this process, small lakes may disappear and be replaced by the plant communities.

  • Halosere: Succession in saltwater marshes.

  • Psammosere: Succession along sand dunes. This stabilizes the dunes and stops them from shifting.

  • Lithosere: Succession starting from bare rock. This is seen most often in lava flows.

  • Xerosere: Succession in dry areas.

  • The species living in a particular place gradually change over time as does the physical and chemical environment within that area.

  • Succession takes place because through the processes of living, growing, and reproducing, organisms interact with and affect the environment within an area, gradually changing it.

  • Each species is adapted to thrive and compete best against other species under a very specific set of environmental conditions. If these conditions change, then the existing species will be outcompeted by a different set of species that are better adapted to the new conditions.

  • The most often quoted examples of succession deal with plant succession. It is worth remembering that as plant communities change, so will the associated micro-organism, fungus, and animal species. Succession involves the whole community, not just the plants.

  • Change in the plant species present in an area is one of the driving forces behind changes in animal species. This is because each plant species will have associated animal species that feed on it. The presence of these herbivore species will then dictate which particular carnivores are present.

  • The structure or 'architecture' of the plant communities will also influence the animal species which can live in the microhabitats provided by the plants.

  • Changes in plant species also alter the fungal species present because many fungi are associated with particular plants.

  • Succession is directional. Different stages in a particular habitat succession can usually be accurately predicted.

  • These stages, characterized by the presence of different communities, are known as 'series'.

  • Communities change gradually from one sere to another. The seres are not totally distinct from each other and one will tend to merge gradually into another, finally ending up with a 'climax' community.

  • Succession will not go any further than the climax community. This is the final stage. 

  • This does not, however, imply that there will be no further change. When large organisms in the climax community, such as trees, die, and fall down, then new openings are created in which secondary succession will occur.

  • Many thousands of different species might be involved in the community changes taking place over the course of succession. For example, in the succession from freshwater to climax woodland.

  • The actual species involved in succession in a particular area are controlled by such factors as the geology and history of the area, the climate, microclimate, weather, soil type, and other environmental factors. 


Bare, inorganic surface → stage 1 colonization → stage 2 establishment → stage 3 competition → stage 4 stabilization → climax community​

​If primary succession starts on dry land it is a XEROSERE
If it starts in water (a pond) it is a HYDROSERE

2.4.U7 During succession, the patterns of energy flow, gross and net productivity, diversity, and mineral cycling change over time

  • Explain how the patterns of energy flow, productivity, diversity, and mineral cycling change during succession.​

In the early stages, gross productivity is low due to the initial conditions and low density of producers. The proportion of energy lost through community respiration is relatively low too, so net productivity is high, that is, the system is growing and biomass is accumulating. In later stages, with an increased consumer community, gross productivity may be high in a climax community. However, this is balanced by respiration, so net productivity approaches zero and the production: respiration (P:R) ratio approaches one.

A disturbance is any event, either natural or human-induced that changes the existing condition of an ecosystem. Disturbances in forest ecosystems affect resource levels, such as soil organic matter, water, and nutrient availability, and interception of solar radiation. Changes in resource levels, in turn, affect plants and animals over time, leading to succession. All of these have an effect of making gaps available that can be colonized by pioneer species within the surrounding community. This adds to both the productivity and diversity of the community.

Changes occurring during a succession

  • the size of organisms increases

  • energy flow becomes more complex

  • soil depth, hummus, water-holding capacity, mineral content, and cycling increase

  • Biodiversity increases and then falls as the climax community is reached

  • NPP and GPP rise and then fall

  • Production: respiration ratio falls

Species diversity in successions

  • Early stages of succession: few species

  • Species diversity increases with the succession

  • The increase continues until a balance is reached between possibilities for new species to establish, existing species to expand their range, and local extinction


2.4.U8 Greater habitat diversity leads to greater species and genetic diversity

  • Explain how succession links to habitat, species, and genetic diversity​

Biological diversity, often shortened to biodiversity, is the variation of life at all levels of biological organization, referring not only to the sum total of life forms across an area but also to the range of differences between those forms. Biodiversity runs the gamut from the genetic diversity in a single population to a variety of ecosystems across the globe.

Greater biodiversity in ecosystems, species, and individuals leads to greater stability. For example, species with high genetic diversity and many populations that are adapted to a wide variety of conditions are more likely to be able to weather disturbances, disease, and climate change. Greater biodiversity also enriches us with more varieties of foods and medicines


2.4.U9 r- and K-strategist species have reproductive strategies that are better adapted to pioneer and climax communities, respectively.

  • ​Compare and contrast r and K strategist species including their roles in succession.

  • Demonstrate how reproductive strategies change between pioneer and climax communities.

  • Distinguish the roles of r and k strategists in succession.

The terms r-selection and K-selection have also been used by ecologists to describe the growth and reproductive strategies of various organisms. Those organisms described as r-strategists typically live in unstable, unpredictable environments. Here the ability to reproduce rapidly (exponentially) is important.  K-strategists, on the other hand, occupy more stable environments. They are larger in size and have longer life expectancies. They are stronger or are better protected and generally are more energy efficient. 

In general, communities in early succession will be dominated by fast-growing, well-dispersed species (opportunist, fugitive, or r-selected life-histories).

As succession proceeds, these species will tend to be replaced by more competitive (k-selected) species. They tend to inhabit relatively stable biological communities, such as late-successional or climax forests

r - selected

  • Short life

  • Rapid growth

  • Early maturity 

  • Numerous and small offspring

  • Little parental care or protection

  • Little investment in individual offspring

  • Adapted to an unstable environment.

  • Pioneers, colonizers

  • Niche generalists

  • Prey

  • Regulated mainly by external factors

  • Lower trophic level

K - Selected

  • Long life

  • Slower growth

  • Late maturity

  • Fewer, but larger offspring

  • High parental care and protection

  • High investment in individual offspring

  • Adapted to a stable environment

  • Later stages of succession

  • Niche specialist

  • Predators

  • Regulated mainly by internal factors (homeostasis)

  • Higher trophic level


2.4.U10 In the early stages of succession, gross productivity is low due to the unfavorable initial conditions and low density of producers. The proportion of energy lost through community respiration is relatively low too, so net productivity is higher that is, the system is growing and biomass is accumulating

  • Discuss the factors that could lead to alternative stable states in an ecosystem.

During succession, Gross Primary Productivity tends to increase through the pioneer and early wooded stages and then decreases as the climax community reaches maturity. This increase in productivity is linked to growth and biomass.

Early seral stages are usually marked by rapid growth and biomass accumulation - grasses, herbs, and small shrubs. Gross Primary Productivity is low but Net Primary Productivity tends to be a large proportion of GPP as with little biomass in the early seral stages respiration is low. As the community develops towards woodland and biomass increases so does productivity. But NPP as a percentage of GPP can fall as respiration rates increase with more biomass.


2.4.U11 In later stages of succession, with an increased consumer community, gross productivity may be high in a climax community. However, this is balanced by respiration, so net productivity approaches 0 and the productivity: respiration (P:R) ratio approaches 1

Succession is the process of ecosystem recovery after some disturbance. Biomass is at maximum in the undisturbed ecosystem; it increases up to this maximum during succession. Plant productivity also grows, especially if the plant cover was destroyed substantially by the disturbance. The productivity of the ecosystem as a whole (i.e. the difference between net primary productivity and its consumption by the ecosystem's heterotrophs) in the process of succession tends to zero. Biodiversity measured as the total number of species in the ecosystem does not change. However, biodiversity measured as the number of species having a substantial population density is lower in the undisturbed ecosystem than in the disturbed one.


2.4.U12 In a complex ecosystem, the variety of nutrient and energy pathways contributes to its stability.

  • ​Explain how complex ecosystems contribute to stability by having a variety of nutrient and energy pathways.

Redundancy in ecosystem structure and function often infer stability on a system. For instance, if there is more than one (redundant) population of microbes that convert ammonium to nitrate and a disturbance wipes out one population, that function (nitrification) will continue to be performed by the remaining populations.

Ecosystem stability is an important corollary of sustainability. Over time, the structure and function of a healthy ecosystem should remain relatively stable, even in the face of disturbance. If stress or disturbance does alter the ecosystem is should be able to bounce back quickly

Stability has two components:

  • Resistance - the ability of the ecosystem to continue to function without change when stressed by disturbance.

  • Resilience - the ability of the ecosystem to recover after disturbance.

Factors affecting stability:

  • Disturbance frequency and intensity (how often and what kind of tillage)

  • Species diversity (intercropping or rotations), interactions (competition for water and nutrients from weed species), and life history strategies (do the species grow fast and produce many seeds or slow with few seeds)

  • Trophic complexity (how many functions are represented), redundancy (how many populations perform each function), food web structure (how do all of these groups interact)

  • Rate of nutrient or energy flux (how fast are nutrients and energy moving in and out of the system or input: output efficiency)

Climatic and edaphic (soil) factors determine the nature of a climax community. Variations in climatic conditions and soil structure greatly affect which plant species can thrive. Human factors frequently affect this process through fire, agriculture, grazing, and/or habitat destruction.

Climatic: temperature, rainfall, winds, and light availability
Edaphic: the presence of soils, pH, water holding capacity, organic matter, and nutrient

Topographic: attitude, slope, aspect, and groundwater
Biological: competition and species interaction, affection of human” fire, grazing, biomass, more k-strategies or fewer r-strategists


2.4.U13 There is no one climax community, but rather a set of alternative stable states for a given ecosystem. These depend on the climatic factors, the properties of the local soil, and a range of random events that can occur over time

  • ​Explain how to climax communities will vary depending on climate, soil, and a range of other local factors.


There is no one climax community. In fact, there are many stable alternatives within an ecosystem. These communities are dependent on:

  • Climatic factors

  • Soil properties

  • Random events

The more complex the ecosystem, the more stable they are due to the variety of nutrient and energy pathways.
If one collapses its overall effect is low as there are many others to takes its place.


2.4.U14 Human activity is one factor that can divert the progression of succession to an alternative stable state by modifying the ecosystem; for example, the use of fire in an ecosystem, the use of agriculture, grazing pressure, or resource use (such as deforestation). This diversion may be more or less permanent depending upon the resilience of the ecosystem.

  • Discuss the range of factors that can divert the progression of succession.

  • Discuss the link between ecosystem stability, succession, diversity, and human activity.

  • Explain how the diversion may end in a permanent or temporary alternative stable state.

  • Discuss how human activity impacts ecosystem stability, succession, and diversity


Human activity is one factor which can divert the progression of succession to an alternative stable state, by modifying the ecosystem, for agriculture, grazing pressure, or resource use such as deforestation. This diversion may be more or less permanent depending upon the resilience of the ecosystem.

Human activities often simplify ecosystems, rendering them unstable, for example, North American wheat farms versus tallgrass prairie. An ecosystems capacity to survive change may depend on diversity, resilience, and inertia


2.4.U15 An ecosystem's capacity to survive change may depend on its diversity and resilience.

  • ​Explain how the resilience of the ecosystem can impact its response to change

​Ecosystem resilience refers to the capacity of an ecosystem to recover from disturbance or withstand ongoing pressures.1 2 It is a measure of how well
an ecosystem can tolerate disturbance without collapsing into a different state that is controlled by a different set of processes. Resilience is not about a single ideal ecological state, but an ever changing system of disturbance and recovery.

Coral reef and other tropical marine ecosystems are subject to frequent disturbances, from threats such as cyclones, crown-of-thorns starfish outbreaks, and influxes of freshwater as well as from a range of human activities. These events often damage, stress, or kill components of the ecosystem. Given enough time, a resilient ecosystem will be able to fully recover from such disturbances and become as biodiverse and healthy as before the impact. Similarly, a resilient ecosystem may be able to absorb the stresses caused by these disturbances with little or no sign of degradation


Application and Skills

2.4.A1 Explain the distributions, structure, biodiversity, and relative productivity of contrasting biomes.

Many places on Earth share similar climatic conditions despite being found in geographically different areas. As a result of natural selection, comparable ecosystems have developed in these separated areas. Scientists call these major ecosystem types biomes. The geographical distribution (and productivity) of the various biomes is controlled primarily by the climatic variables precipitation and temperature..

Most of the classified biomes are identified by the dominant plants found in their communities. For example, grasslands are dominated by a variety of annual and perennial species of grass, while deserts are occupied by plant species that require very little water for survival or by plants that have specific adaptations to conserve or acquire water.

The diversity of animal life and subdominant plant forms characteristic of each biome is generally controlled by abiotic environmental conditions and the productivity of the dominant vegetation. In general, species diversity becomes higher with increases in net primary productivity, moisture availability, and temperature.

Adaptation and niche specialization are nicely demonstrated in the biome concept. Organisms that fill similar niches in geographically separated but similar ecosystems usually are different species that have undergone similar adaptation independently, in response to similar environmental pressures. The vegetation of California, Chile, South Africa, South Australia, Southern Italy, and Greece display similar morphological and physiological characteristics because of convergent evolution. In these areas, the vegetation consists of drought-resistant, hard-leaved, low growing woody shrubs and trees like eucalyptus, olive, juniper, and mimosa.


2.4.A2 Discuss the impact of climate change on biomes.

Sea ice and glaciers are melting all over the globe due to warmer temperatures. Over 60% of the world's freshwater is stored in the ice sheets covering Antarctica. The Ross ice shelf in Antarctica alone is as large as France. The average temperature on the Antarctic Peninsula has risen significantly since 1947. All of the major floating ice shelves are shrinking - melting more during the summer than is being refrozen during winter - about 8,000 sq. km have been lost since the 1950s. If the West Antarctic ice sheet to melt due to climate warming, it could raise sea levels by 6 meters. Sea levels are already rising by 2mm a year - faster than during the past 5,000 years Krill - small shrimp-like sea creatures that are a major food source for seals, whales, and penguins - feed on algae found on sea ice. In Antarctica, they are concentrated northeast of the Antarctic Peninsula - but have declined 80% since the 1970s


2.4.A3 Describe the process of succession in a given example.

  • ​Use a case study to describe the pattern of change in the plant communities during succession.


Carrizozo New Mexico Lave Flow

Lava from an erupting volcano incinerates everything in its path and forms new land that is made from inorganic material. While it is rich in minerals, the land cannot support a varied and complex ecosystem. Its capacity to sustain a stable ecosystem is limited. Pioneer species that colonize areas after volcanic eruptions include sword fern and green algae

​A few small invertebrate animals may also venture into this territory, followed by crickets and spiders.

In the case of volcanic eruptions in the ocean, the atolls formed are isolated from other terrestrial ecosystems and have unique food chains and webs. Pioneer species often arise from spores carried through ocean currents.


2.4.A4 Explain the general pattern of change in communities undergoing succession

  • The size of the organisms increases with trees, creating a more hospitable environment.

  • Energy flow becomes more complex as simple food chains become complex food webs.

  • Soil depth, hummus, water-holding capacity, mineral content, and cycling all increase.

  • Biodiversity increases because more niches (lifestyle opportunities) appear and then falls as the climax community is reached.

  • NPP and GPP rise and then fall.

  • Productivity: Respiration ration falls.


2.4.A5 Discuss the factors that could lead to alternative stable states in an ecosystem.

Ecosystems can shift from one state to another due to changes in the ecosystem. These changes are quantities that change quickly in response to feedback from the system (i.e., they are dependent on system feedbacks), such as population densities. This perspective requires that different states can exist simultaneously under equal environmental conditions These will depend on:

  • Climatic factors

  • Soil properties

  • Random events

You need to be able to discuss the factors which could lead to alternative stable states in an ecosystem, and discuss the link between ecosystem stability, succession, diversity, and human activity.

2.4.A6 Distinguish the roles of r and K selected species in succession.


What influences survivorship rates:

  • competition for resources

  • adverse environmental conditions

  • predator-prey relationships


Example of the survivorship curve:

  • curve for species where individuals survive for their potential life span and die at the same time. Salmons/humans (K-strategists)

  • curve for species where individuals die young but who survive lives very long life turtles/ oysters. (r-strategists)



2.4.S1 Analyse data for a range of biomes

​Industrial air pollution from the developed world is carried on the dominant wind currents up to the arctic. After settling onto the tundra, snow, and ice it is absorbed into the food chain. The people and creatures there have some of the highest concentrations of toxins in their bodies of anywhere on earth.


2.4.S2 Interpret models or graphs related to succession and zonation.

Classroom Materials
World Map - Blank
The Biome Map questions and Instructions
Biome Comparison Project
Biome Matrix
Climatograph Biomes_worksheet
Construction Climate graphs worksheet
The Disappearing Rain-forest article
Succession and Zonation Cards activity
Savannah Succession activity
r and k Strategists review worksheet

Case Studies
Mountain altitude zonation
Mt. Saint Helen
Abandon car lot
Amazon Rainforest


Useful Links
2.4 Biomes" by NicheScience
2.4 Zonation and Succession" by NicheScience 
2.4 r-K Strategists and Succession" by NicheScience
Blue Planet
The World's Biomes - Berkeley University
Land Biomes - About Biology
Aquatic Biomes - About Biology
Biomes Animation - McGraw-Hill
Terrestrial biomes - Berkeley University
Biomes and Ecosystems - Window 2 The Universe
Interactive Biomes - Marietta College
Biome Game - Earth Observatory
Global Ecology - The Global Education Project
Introduction to Biomes - Earth Labs
Rebuilding a Rainforest from Scratch - Scientific America
Biomes and Climate Graphs


This activity, prepared by TES, will help you better understand the relationship between temperatures, precipitation and specific biomes.
Survivorship Curves
r and K Strategies Animation - McGraw Hill
Primary Succession animation - yTeach
Mt St. Helen's
Primary and Secondary Succession - GeoWords
An Example of Secondary Succession - Wiley
Succession: A Closer Look. -  Nature
Example Secondary Succession - Offwell Woodland and Forest Trust
Succession Case Studies - Marietta College
Life After People - History

In The News
Rainforest Reduction - BBC Travel 02 November 2012
Amazon Rainforest: The Earth's Lungs - BBC Future 27 February 2013
Ecological Services of Mangrove Forests - BBC Future 13 February 2013
Nutrients from Deserts - BBC Future 6 February 2013

Climate plays an important role in the development of biomes. Robert Whittaker, an American ecologist, plotted rainfall vs. temperature for points all over the globe on a single graph (see below).  He then looked at what biomes had developed at those sites and was able to group the different biomes according to mean annual temperature and precipitation, as the shaded areas in the graph below indicate.


Note that in Whittaker's diagram the temperature axis is reversed; that is temperature goes DOWN as you move to the right.   Theoretically, if you know the average temperature and precipitation for a site,  you should be able to predict what biome will develop there.


  • Zonation occurs on different scales that can be both local and global


Theory of knowledge:

  • Ecosystems are studied by measuring biotic and abiotic factors—how can you know in advance which of these factors are significant to the study?


Video Clips

This HD dramatic video introduces you to the Biomes of Earth









































Planet Earth Episode 1 From Pole to Pole | BBC Documentary














In this video, Paul Andersen describes both weather and climate. Weather is the day-to-day conditions on the Earth's surface, including temperature, wind, humidity, air pressure, and precipitation. Climate is the long term condition on the Earth's surface. Both climate and weather are determined by sunlight, water, landforms, and life forms
















he Ocean is essential to life on Earth. Most of Earth's water is stored in the ocean. Although 40 percent of Earth's population lives within, or near coastal regions- the ocean impacts people everywhere. Without the ocean, our planet would be uninhabitable. This animation helps to convey the importance of Earth's oceanic processes as one component of Earth's interrelated systems.














Global circulation on our rotating Earth splits the atmosphere into three cells in each hemisphere: the Hadley cell, Ferrel cell, and Polar cell. In this video, we look at how air moves around each cell and how this controls the location of the world’s deserts and rainforests












In this third, and final, video in the Global Circulation series we look at how the rotation of the Earth influences our winds through the Coriolis effect and gives us jet streams and prevailing wind patterns.














Satellite-based passive microwave images of the sea ice have provided a reliable tool for continuously monitoring changes in the Arctic ice since 1979. Every summer the Arctic ice cap melts down to what scientists call its "minimum" before colder weather begins to cause ice cover to increase. The ice parameters derived from satellite ice concentration data that are most relevant to climate change studies are sea ice extent and sea ice area. This graph displays the area of the minimum sea ice coverage each year from 1979 through 2013. In 2013, the Arctic minimum sea ice covered an area of 4.704 million square kilometers.














Paul Andersen explains the differences between an r and a K selected species. He starts with a brief description of population growth noting the importance of; r or growth rate, N or number of individuals in the population, and K the carrying capacity. He describes three different survivorship curves found in organisms. He lists the characteristics of r-selected species like bacteria and K-selected species like humans.













Review of some basic properties of the marine intertidal ecosystem












In the world of ecology, the only constant is change - but change can be good. Today Hank explains ecological succession and how ecological communities change over time to become beautiful, biodiverse mosaics.












Discover a process that truly demonstrates nature's grit: ecological succession! 














Paul Andersen describes the process of ecological succession. During this process, life reestablished itself after a disturbance. During primary success, all of the material is removed including the soil. For example during a volcanic eruption, all traces of life are removed. However, during secondary success, the soil remains intact. An example of secondary success is wildfires.











The ecosystem of Mount St. Helens continues to recover 30 years after the May 18, 1980 eruption













Succession, disturbances, and the difference between man-made and natural disturbances and how landowners can use disturbance practices to mimic nature.












Fire ecologist and Ph.D. candidate Emily Booth discusses the future of the Lost Pines of Bastrop State Park, as well as her role in cataloging the forest's recovery














Biomes, Zonation, & Succession (2.4)

For Succession Click Here



What Causes a Biome?

 3 Major Factors determine the distribution of Biomes: Insolation, Precipitation, and Temperature (all 3 are major factors in climate) 

The Tricellular Model of atmospheric circulation- a simplified model widely used but recognized as inaccurate (Understanding global precipitation patterns)
Global Circulation (video 1)
Global Atmospheric Circulation (video 2) 
Description of the Tricellular Model (good explanations)​
Three cell system

​Texas Database P/E ratio Activity
Precipitation and Evaporation Database ----- ​Excel File with usable data
​Drought data from 2011- 2016 for Texas
El Nina/ El Nino year dates



Biomes/ Ecosystems change as abiotic factors change within an area 


Biome Data

World Biomes
Terrestrial Biome information
Characteristics of Biomes
World Biome Data - activity handout
Biome + World Map - Handout



Succession Notes

Ecological Succession- good overview
Ecological Succession: Change is good - Crash Course
Climax Communities- video

GPP/NPP and Succession
Soil Fungi importance
Soil Biology Primer- Understanding Soil


Mount St. Helen's Eruption 
Life Returns to Mt. St. Helen's
Mt. St. Helen's Ecosystem 
Life After Mt. St. Helen's  (full documentary)

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