Geoecology

Biomes

A biome is a unique world region that is controlled by climate. It has four unique characteristics:

• Climate
• Soil
• Flora (vegetation)
• Fauna (animals)

Climate is the most important characteristic as it determines what type of soil is located there, what plants grow and what animals can survive.

Animals and plants have evolved body parts and ways of living to enable them to survive in their biome. This is called adaptation.

Traditionally a biome is named after the vegetation in the area, e.g. Rainforest biome, taiga biome (taiga forest)

Exam:

• Questions can focus on describing characteristics in general, describe how they link together and influence each other or how plants and animals have adapted to the biome

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Biomes

Figure 1: Location of biomes

Marking Scheme

• The question on Biomes will be worth 80 marks so will require a longer answer than the normal 30-mark essays. It should take approximately 3-4 pages to answer.

• Don't get overwhelmed by this – when you break down the marking scheme it makes it easier

• Each paragraph in this essay will be on a different aspect of the answer – each paragraph will resemble as a mini essay, building a coherent answer to the question.

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Number of aspects	3 @ 20 marks each	4 @ 15 marks each
Identifying aspect	4 marks	3 marks
Discussion	8 x SRPs	6 x SRPs
Overall Coherence	20 marks graded	20 marks graded

Marking Descriptors Overall Coherence (OC):

In awarding Overall Coherence (OC) the examiner will consider how well the candidate deals with the set question and will follow the following marking descriptors:

Overall Coherence (20 marks)

Excellent	20	Excellent ability to relate knowledge to the set question. Excellent, comprehensive response demonstrating detailed knowledge of subject matter.
Very Good	17	Considerable strength in relating the knowledge to the set question. Very good response demonstrating very broad knowledge of the subject matter.
Good	14	Reasonable capacity to relate knowledge appropriately to the set question. Good response with worthwhile information. Broad knowledge of the subject matter demonstrated.
Fair	10	Some effort to relate knowledge to the set question. Some relevant information presented but insufficient application of information to set question.
Weak	6	Very limited engagement with set question. Identified some relevant information.
Poor	0	Failure to address the question resulting in a largely irrelevant answer.

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2018

• Climate and Soil characteristics in one Biome and their impact on vegetation

2016

• Examine characteristics of one biome with reference to three characteristics – all four were listed

2015

• Examine how plants and animals adapted to climate and soil conditions in one biome you have studied

2013

• Account for the type of climate in one biome you have studied and explain how this climate impacts on the soil and vegetation in that biome

2011

• Examine characteristics of one biome with reference to three characteristics – all four were listed (same as 2016)

2010

• Examine influence of climate on characteristics of one biome you studied (none listed)

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Essays for this section

Prepare two essays for this section

1. Characteristics of biomes (climate, soil, flora, fauna)

2. Plant and animal adaption to climate and soil

Sample Layout

1. Characteristics of biomes (climate, soil, flora, fauna)

Intro: Name biome, name characteristics (give layout of the essay), brief explanation/general info on biome

Aspect 1: Climate

Aspect 2: Soil

Aspect 3: 'Flora and Fauna' OR Flora or Fauna

Concluding Sentence: One brief line to fit the question e.g. 'it is clear that climate influences other characteristics such as...'

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2 Plant and animal adaption to climate and soil

Intro: Name biome, name characteristics (give layout of the essay), brief explanation/general info on biome

Aspect 1: Climate and soil characteristics

Aspect 2: Flora adaption to climate and soil

Aspect 3: Fauna adaption to climate and soil

Concluding Sentence: One brief line to fit the question e.g. 'it is clear that climate influences other characteristics such as..' 'it is clear that the plants and animals have used various techniques to adapt and survive in the Amazon rainforest'

The Tropical Rainforest Biome

General info

• Forest of tall trees found in the hot, wet, tropical zone around the earth – also called the jungle
• Home to the greatest variety of living things (biodiversity) in the planet due to its warm, sunny and humid tropical climate
• Tropical rainforests produce about 30% if the worlds fresh water through transpiration

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• Covering less than 2% of the earth's surface, rainforests are home to about half of all living things on the planet

• Estimated that a typical patch of rainforest measuring 6km2 contains 1,500 species of flowering plants, 750 species of tree, 400 species of bird, 150 species of butterfly, 100 species of reptile and 60 amphibian species

Uses

• Provides many foods such as bananas, peppers, cashews, peanuts, coffee and tea

• Fibres from trees are used in rugs, rope and string. Tropical forest oils are used in cosmetics, shampoos and perfumes

• Life-saving medicine such as aspirin (pain relief) and two-thirds of all medicines found to have cancer-fighting properties come from rainforest plants

Location

Three main areas:

• Central America and the Amazon Basin (Brazil)
• Africa-Congo Basin
• Indo-Malaysia

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Characteristics of the rainforest biome

1 Climate

• Tropical climate, meaning it is hot, wet and humid all year round
• There is almost 12 hours of sunshine every day as the sunlight hits the region at a 90° angle, resulting in intense heating with average temperatures around 27°C
• There is a small temperature range as the hours of sunlight does not vary between summer and winter
• Due to the intense heating, large amounts of moisture evaporates from the ground and vegetation

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• Each tree has the potential to release over 755 litres of water every year through the process of transpiration – the evaporation of water on the leaves of a plant.

• This results in heavy convectional rainfall as the water vapour rises, cools and condenses

• An average of 1,250mm to 6,600mm of rain falls in the rainforest each year

• This amount of precipitation leads to high humidity levels of 77%-88%

• Rainfall in the rainforest is very different to other environments – usually water vapour blows away and falls in other areas.

• In the rainforest half of the precipitation comes from the forest's own evaporation (trees releasing moisture through transpiration), meaning that it falls straight back down to the land again in a continuous cycle

• The tropical climate is responsible for the variety of living things (biodiversity) in the rainforests as the plants grow well and there is plenty of food for animals

  • The long hours of sunlight are trapped by the plants and converted into energy

  • These plants are then eaten by animals

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2 Soils

• The latosol is the soil most associated with the tropical rainforest biome

• Chemical weathering and leaching played an important role in its formation meaning it lacks nutrients

• Thousands of years of heavy convectional rainfall washed away the nutrients through leaching

• Nutrients are not present in the soil and are instead found in living plants and the layer of decomposing plant litter on the ground (O horizon)

• A study in the amazon rainforest found that 99% of nutrients are found in the roots in the forest floors

• The large variety of insects, bacteria and fungi act as decomposers, quickly turning plant and animal matter into humus (humification)

• As soon as these nutrients are released into the soil by humification, the plants intercept them at the O horizon – if they went deeper than this then they would be washed away through leaching

• As a result, the rainforest has a short nutrient cycle – a few days separate the dead organic matter being converted into humus and being absorbed by plant roots

• When a rainforest is burned or cut down, the source of nutrients is removed – it quickly becomes depleted of all nutrients and can no longer be used

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• Laterite soils can develop from poor soil management such as deforestation combined with intense heat and precipitation

• Laterite soils are hard, brick like soils that are impossible to cultivate, even when wet

• They are formed when high temperatures bake the exposed soil, creating a hard, impermeable surface

Vegetation/Flora

• Tropical rainforests have a huge variety of vegetation with the three largest rainforests (South American, African and Asian) having different plant groups and animal species

• Plant species look similar and trees can often only be distinguished by the flowers that grow on them

• Typical rainforest trees include teak, mahogany, palm oil and brazil nut trees – on average it takes 60 years for these trees to grow enough to be cut

• The hot, humid conditions and the long hours of sunlight (12 per day) are perfect for plant growth

• Plants in the rainforest have evolved into a unique four-layered structure in order to avoid competition for sunlight and moisture – each plant species has adapted to survive in a specific layer, allowing for thousands of different species to grow and thrive together

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The four layers are: Emergent layer, Canopy layer, Understorey layer and Forest Floor

Emergent layer

• Consists of the tops of the tallest trees – 40m to 80m in height

• These trees have small, pointed leaves as they are exposed to drying winds that can decrease humidity

• They also have straight, smooth trunks with very few branches. They have a shallow root system but grow buttresses to support their weight. These can be up to 9m wide

• Home to animals such as the scarlet macaw and insects

Canopy

• Upper parts of trees below the emergent layer – 20m to 40m in height

• Plants in this layer include thick vines and tree-living plants called epiphytes such as mosses and orchids

• Leaves are large in order to catch as much sunlight as possible

• Full of animal life with many species of insects, spiders and birds. There are also mammals such as the howler monkey (2nd loudest animal in the world after the blue whale) and the orangutan

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Understorey

• Dark environment underneath the canopy
• Very little sunlight reaches the understorey, so plant growth in this layer is limited
• Plants include shrubs, small trees and vines, all of which have adapted to little sunlight and poor soil
• Trees receive the most sunlight and have large leaves to trap this light
• Animals include beetles, insects, spiders and mammals such as the jaguar who spend a lot of time on the branches of trees looking for prey

Forest Floor

• The forest floor only receives 3% of the sunlight that hits the top of the emergent layer
• It consists of the bottom 2m of the forest and is very dark
• Very few plants can grow and survive in this layer
• Generally, it is only possible for plants to grow here if a tree falls, creating a clearing for sunlight to come through
• Largest animals live here – gorillas, anteaters, tapirs, jaguars – as well as indigenous people such as the Yanomami of Brazil

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Figure 3

Animals

• A tropical rainforest contains more than 100 different species in each hectare

• The south American rainforest, around the Amazon Basin, contains a higher amount of biodiversity than any other biome in the world. In this biome, there is nearly 30 million species of insects, 1,600 species of birds and 2,500 species of fish.

• Every species has evolved in a particular way in order to avoid competition for food and living space.

• Every species has evolved in a particular way in order to avoid competition for food and living space.

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• Very few animals move between layers of the forest and many don't touch the forest floor, such as the flying squirrel and the tree frog. Most animals tend to be small due to this arboreal (tree-living) lifestyle.

• Many animals have also adapted in order to hide from potential predators. Insects disguise themselves to look like twigs (stick insects) or leaves. The sloth has fur that is covered in moss and algae which helps them to hide from predators while they hang from the canopy.

Figure 4: Howler Monkey

Figure 5: Howler Monkey

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Plant and Animal Adaptations to the Rainforest Biome

As there are so many different plants and animals in the rainforest biome, there is great competition for food, sunlight and nutrients. Plants and animals have had to develop special features in order to adapt and survive in this environment.

Plant adaptations to climate and soil

Plant adaptations can be grouped under three headings – leaves; roots and trunks; parasitic plants.

1 Leaves

• Plants must adapt to large amounts of precipitation falling on their leaves (30mm per day) and fungal attack from the warm, humid conditions (27°C and 88% humidity)

• Many plants have flexible leaves that bend easily. This prevents them from breaking when they are weighed down with water, instead aiding the run off of water

• Other leaves have holes in them or drip tips which funnel the water off of them

• Some plants have grooved leaves which funnel water to their roots whilst others have oily coatings to resist fungal attack

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• Plants on the forest floor have large leaves as very little sunlight reaches down that far (3%). This allows them to absorb as much light as possible. Trees in the canopy have smaller leaves as they are exposed drying wind – they are smaller, pointed and narrower

• Many tree species have saplings that grow large leaves when they are young in the understorey and then produce smaller leaves when they reach the direct sunlight of the canopy

2 Roots and Trunks

• Trees have straight trunks and do not grow branches until they are 30 metres high – the lack of sunlight below the canopy means there is no need to grow branches

• Emergent layer trees such as mahogany have adapted to the competition for sunlight by growing extremely tall

• These trees must also cope with the infertile latosol soil – all the nutrients are held close to the surface, so trees have shallow roots in order to access these nutrients

• These roots develop in the form of buttress roots, spreading out over the surface in order to support the weight of the tree and father nutrients

• Most trees have thin, smooth barks (1-2mm) as they don't need to protect themselves from water loss and freezing temperatures due to the hot, wet, humid tropical climate

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• The thin bark also means that it is difficult for plant parasites to catch hold of the trunks of trees

• Many plants in the upper layers of rainforests have aerial roots called epiphytes that use the moisture in the air such as orchids and ferns

  • Their sponge like roots gather water and soak it up for later use

  • They produce fleshy fruit which birds, insects and other animals feed on

Parasitic Plants

• Examples include vines and lianas – over 2,500 species of vines and lianas

• They have adapted to the lack of sunlight on the forest floor by attaching themselves to trees in order to reach the sunlight – lianas attach themselves to young saplings and grow with them as they move through the layers

• They live off of the nutrients supplied by the host plant

Figure 6: Buttress Roots

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Animal adaptations to climate and soil

• The conditions of the rainforest biome are perfect for animal survival – warm, shelter from heat, no shortage of water but shelter from rain and no seasons which could lead to food shortages.

• However, due to overcrowding there is huge competition for living space and food. Animals have indirectly adapted to the climatic and soil conditions of the tropical rainforest biome in order to survive – each animal has adapted to living in a particular layer of the forest.

Adaptations can be grouped into three headings – camouflage, body structure, animal-plant relationships

1️⃣ Camouflage/colour

• One of the most effective adaptations, used by many different species of animals

• The forest floor is covered with plant litter such as twigs and leaves so many animals such as moths, stick insects and chameleons use this method of adaption

• The Giant Leaf Frog has adapted by having green skin and an irregularly shaped body outline which looks like a leaf – this makes it hard for predators to see them

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• Other animals such as the jaguar has spotted coats to help them blend in to their surroundings

• Animals use the colour of their skin to warn potential predators that they are poisonous – some animals are only bluffing and are completely harmless, but others are definitely not, such as the poison arrow frog

• The poison arrow frog comes in many different colours, from sky blue to black and green. The secretion from its skin is used by rainforest tribes to poison the tips of their blow-gun darts

• The Brazilian Tree Sloth lives completely in the canopy layer, sometimes even on just one tree. They move very slowly and have a very slow metabolism, enabling them to survive on the low energy content of the leaves it eats

  • They are covered in a green layer of algae and moss which camouflages its fur in its arboreal (tree-living) environment
  • It has large eyes to see in shady conditions and have long hooked claws to allow them hang easily from branches

• Many animals must adapt to living in trees and must be good climbers or fliers

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• Flying squirrels have evolved flaps of skin between their front and back legs, allowing them to jump between trees and glide for longer distances

• Lemurs and spider monkeys have prehensile tales, meaning they can wrap around a tree branch

• Geckos can flatten their bodies onto tree bark as protection against predators

• The hooked beaks of macaws and other parrots allow them to open nuts easily whilst also acting as an extra foot when climbing

Animal-Plant Relationships

• Animals have become very specialised in order to avoid competition for food – they adapt to eat a specific plant or animal that few others eat. Animals depend on plants for food and plants depend on animals to disperse their seeds

• Insects and hummingbirds are attracted to the Ceiba tree and its bright red flowers

  • These animals drink the nectar, collect the pollen and fertilise the tree

• Leafcutter ants climb tall trees and cut small pieces of leaves to carry back to their nest

  • The ants bury these leaves and the combination of the leaves and the ant's saliva encourages fungus to grow which is the only food the ant eats