2.4 - Biomes, Zonation And Succession Flashcards
Define biome
Biomes are large-scale ecological communities that are characterised by their dominant vegetation, climate, and other abiotic factors that shape their biotic communities
What are the 5 classes of biomes
Aquatic
Forest
Grassland
Desert
Tundra
What is a aquatic biome
Aquatic biomes are water-based ecosystems that are divided into freshwater and marine ecosystems, including lakes, rivers, oceans, and coral reefs
What is a forest biome
Forest biomes are dominated by trees and are categorised into tropical rainforests, temperate deciduous forests, and boreal forests
What is a grassland biome
Grassland biomes are characterised by grasses and herbaceous plants and are categorised into savannas and temperate grasslands
What is a desert biome
Desert biomes are characterised by low rainfall and are dominated by cacti and other drought-resistant plants - they can be further divided into subcategories such as hot deserts, cold deserts, coastal deserts, and semi-arid deserts
What is a tundra biome
Tundra biomes are found in high latitudes and are characterised by low temperatures and permafrost - they can be further divided into subcategories such as arctic tundra and alpine tundra
What is a limiting factor
A limiting factor is anything (biotic and abiotic) that restricts, slows or stops organisms from growing. Examples include food, competition, temperature, altitude, and available sunlight.
What affects the productivity and biodiversity of a biome
Limiting factors
What is the limiting factor in a desert
Water as it affects plant growth, while in a tundra, low temps and permafrost limit plant growth
What is the location of a tropical rainforest
- low latitudes
- Within the Tropics 23.5° north and south of the equator
- amazon in South America, New Guinea, Southeast Asia, Zaire basin
What is the annual precipitation in a tropical forest
Over 2000 mm
What is the temperature range in a tropical forest
26-28 degrees
What are the seasons in a tropical rainforest
No seasons: hot and wet all year round
What is the growing season in a tropical rainforest
All year round
What are the soil type in a tropical rainforest
Infertile due to leaching and rapid uptake of nutrients by plants
What is the biodeiversity in a tropical rainforest
Approx. 50% of the world’s plant and animal species live within the rainforest biome
Four layers of vegetation: mahogany, teak trees, lianas, orchids
Toucans, jaguars, frogs, snakes
Where is the savanna
North and south of the tropical and monsoon forest biomes 5° - 30° north and south of the equator
Central Africa - Tanzania, Kenya
What is the annual precipitation in the savanna
800-900 mm
What is the temperature range in the savanna
15 - 35 degrees
What are the seasons in the savanna
Wet and dry season
What is the growing season in the savanna
During the wet season
What are the soils like in the savanna
Free draining with a thin layer of humus
Not very fertile most nutrients near the surface
What is the biodiversity like in the savanna
Wide range of plant and animal species
Grasses, baobab and acacia trees
Zebras, elephants, giraffes
Greatest diversity of hoofed animal
What is the location of a hot desert
15 - 30 degrees north and south of the equator
North Africa - Sahara, Southern Africa - Kalahari and Namib, Australia, Middle East
What is the annual precipitation in a hot deseret
Bellow 250 mom
What is the temp range in a hot desert
Daytime temperatures can reach 50°C but average around 25°C
Night time temperatures below 0°C
What are the seasons in a hot desert
Summer and winter
What is the growing season in a hot desert
All year round
What are the soils like in a hot desert
Infertile
What is the biodiversity like in a hot desert
Low diversity
Cacti, yucca
Spiders, scorpions, camels, meerkats
What is the location of a tundra
North of the artic circle and antártica
What is the annual precipitation in a tundra
Less than 250 mm
What is the temp range in a tundra
Below 0°C for 6-10 months
What are the seasons for a tundra
Winter and summer
What is the growing season for a tundra
6-10 weeks
What are the soils like in a tundra
Thin infertile soil
Permafrost
What is the biodeiversity like in a tundra
Low biodiversity
Snowy owls, snow bunting and tundra swan
Arctic foxes, hares and wolves
Polar bears, musk ox and caribou
Small grasses, mosses, lichen
What impacts the distribution of biomes
Insolation, precipitation, and temperature are the main factors governing the distribution of biomes
- Insolation refers to the amount of solar radiation that reaches the Earth’s surface and affects temperature
- Precipitation affects the availability of water, which is a key limiting factor for many biomes
- Temperature determines the rate of photosynthesis and respiration in plants, as well as the metabolic rates of animals
DO QUESTION ON SAVE MY EXAMS
How is climate change affecting the distribution of biomes
As the global climate changes, the distribution of biomes is shifting, leading to significant impacts on ecosystems and the services they provide
What are the 2 ways biome shift can occur
Range shifts
Biome type changes
What is a range shifts
when species move to new areas to find suitable conditions as their current habitats become less hospitable
What is a biome type changes
when a biome transitions to a different type, such as a forest becoming a savanna or a tundra becoming a forest
What determines the distribution of a biome
Temperature and precipitation
What does changes in global temperature do to the size of biomes
This means that the warmer biomes, such as tropical rainforests and savannas, are expanding, while the colder biomes, such as tundra and boreal forests, are contracting
What are the impacts of biome shifts
- As species move to new areas or experience changes in their habitats, they may face new competition, predation, or disease
- This can lead to declines in population numbers and even extinction in some cases
- Biome shifts can also have impacts on the vital services that ecosystems provide to living organisms, especially humans, such as water regulation, nutrient cycling, and carbon sequestration
What is the global atmospheric circulation
The global atmospheric circulation can be described as a worldwide system of winds moving solar heat energy from the equator to the poles to reach a balance in temperature
How is wind formed
From areas of high pressure to areas of low pressure and this movement generates wind
What causes a pressure difference
Due to the sun heating the earths surface unevenly
Define isolation
Insolation is a contraction of the words INcoming SOLAr radiaTION. This is the incoming shortwave radiative energy received from the sun and varies at different times and places.
Where is isolation greatest in the world
Insolation that reaches the Earth’s surface is greater at the equator than at the poles due to the Earth’s curvature and angle of the Earth’s tilt
LOOK AT ANGLE OF ISOLATION DIAGRAM
How are weather patterns generated
- Hot air rises and cooler air sinks through the process of convection
- This irregular heating of the Earth’s surface creates pressure cells
- Each cell generates different weather patterns
How are the three atmospheric cells created
Air movement within the cell is roughly circular and moves surplus heat from equatorial regions to other parts of the Earth
In both hemispheres, heat energy transfer occurs where 3 atmospheric circulation cells meet
What are the names of three cells
Hadley, Ferrell and polar cells
What is the Hadley cell
- Hadley cell is the largest cell and extends from the equator to between 30° and 40° north and south
- Trade winds blow from the tropical regions to the equator and travel in an easterly direction
- Near the equator, the trade winds meet, and the hot air rises and forms thunderstorms (tropical rainstorms)
- From the top of these storms, air flows towards higher latitudes, where it becomes cooler and sinks over subtropical regions
- This brings dry, cloudless air, which is warmed by the Sun as it descends: the climate is warm and dry (hot deserts are usually found here)
What is the Ferrell cell
The middle cell
- This is the most complicated cell as it moves in the opposite direction from the Hadley and Polar cells; similar to a cog in a machine
- Air in this cell joins the sinking air of the Hadley cell and travels at low heights to mid-latitudes where it rises along the border with the cold air of the Polar cell
- This occurs around the mid-latitudes and accounts for frequent unsettled weather
What is the polar cell
The smallest cell
- Air in these cells is cold and sinks creating high pressure over the highest latitudes
- The cold air flows out towards the lower latitudes at the surface, where it is slightly warmed and rises to return at altitude to the poles
Define zonation
Zonation in ecology refers to the gradual change in the composition of species and communities across a landscape, based on a gradient of environmental factors
What factors affect zonation
- altitude
- latitude
- temperature
- moisture
- light
What happens as the enviromental factors change. How does the impact zonation
As these factors change, the species present in an ecosystem also change, leading to distinct zones or bands of organisms that can be observed in the ecosystem
- This process occurs due to the interactions between the physical environment and the biological components of an ecosystem
Use the example of a rocky intertidal zone to explain zonation
- At the highest point (sometimes referred to as the spray zone), the zone is usually dry and dominated by lichen and other hardy plants that can withstand long periods of exposure to air and sunlight
- In the high tide zone, the environment becomes more hospitable for other organisms such as barnacles, mussels, chitons, limpets and sea snails that can attach themselves to the rocks and withstand waves
- Further down towards the low tide zone, the environment becomes even more favourable for marine organisms such as sea stars, anemones, and sea urchins that require the constant presence of water
What is succession
The process of a ecosystem changing from being simple to compete
What happens during succession
The biotic conditions and abiotic conditions change over time
What happens to the species numbers during succession
Succession is the process that occurs when newly formed or newly exposed land (with no species present) is gradually colonised (inhabited) by an increasing number of species
How can uninhabited land be created
- The magma from erupting volcanoes cools and often leads to the formation of new rock surfaces or even new rocky islands in the sea
- Another way new land can be exposed is by sea-level dropping or the drying up of a lake, leaving areas of bare rock
What are some examples of where succession can occur
- Sand dunes in coastal areas
- Marram grasses are the pioneer species in these environments as they have deep roots to access water that other plants can’t reach and they are also able to tolerate the salty environment i.e. the high concentrations of sodium and calcium ions caused by sea spray
Describe the first stage of succession
seeds and spores that are carried by the wind land on the exposed rock and begin to grow
- These first species to colonise the new land (often moss and lichens) are known as pioneer species
- As these pioneer species die and decompose, the dead organic matter (humus) forms a basic soil
What is the second stage of succession
Seeds of small plants and grasses, sometimes also carried in the wind or sometimes transported other ways (e.g. in bird faeces) land on this basic soil and begin to grow (these smaller plants are adapted to survive in shallow, relatively nutrient-poor soils)
- As these small plants and shrubs die and decompose, the new soil becomes deeper and more nutrient-rich
- The roots of these small plants and shrubs also form a network that helps to hold the soil in place and prevent it from being washed away
What is the third stage of succession
Larger plants and shrubs, as well as small trees, that require deeper, more nutrient-rich soil, can now begin to grow
- These larger plants and small trees also require more water, which can be stored in deeper soils
What is the final stage of succession
Finally, the soil is sufficiently deep, contains enough nutrients and can hold enough water to support the growth of large trees
- These final species to colonise the new land become the dominant species of the now relatively complex ecosystem
- The final community formed, containing all the different plant and animal species that have now colonised the new land, is known as the climax community
Define climax community
The stable, final community that exists in a balanced equilibrium and that makes up the final stage of succession. Abiotic factors are more or less constant over time.
What factors change as the structure and species composition changes during succession
patterns of energy flow, productivity, diversity, and mineral cycling that ecosystem
How does energy flow change during succession
- During the early stages of succession, the energy flow in the ecosystem is relatively low
- This is because there are only a few species present, and most of the energy is used to build biomass
- As the ecosystem becomes more complex, energy flow increases
How does gross and net productivity change during succession
- During the early stages of succession, gross productivity and net productivity is low because there are only a few species present so the ecosystem’s overall gain in energy and biomass per unit area per unit time is relatively small
- As the ecosystem becomes more complex, gross productivity and net productivity increase
How does diversity change during succession
- Diversity refers to the number of species present in an ecosystem
- During the early stages of succession, diversity is low because there are only a few species present
- As the ecosystem becomes more complex, diversity increases because there are more niches available, and more species are able to coexist within the same habitats in the ecosystem
How does the mineral cycle change during succession
- Mineral cycling refers to the movement of nutrients through an ecosystem
- During the early stages of succession, mineral cycling is relatively simple as there are only a few species present and nutrient cycling is largely driven by abiotic processes
- As the ecosystem becomes more complex, nutrient cycling becomes more complex because there are more species present and each species has unique nutrient requirements and cycling processes
What is a pioneer community
- In pioneer communities (i.e. in the early stages of succession), gross productivity is low due to the unfavourable initial conditions and low density of producers (low gross primary productivity)
- However, the proportion of energy lost through community respiration is also relatively low
- This means that net productivity in pioneer communities is relatively high
- This allows the pioneer community system to grow and accumulate biomass
What is a climax community’s productivity
In climax communities (i.e. in the later stages of succession), gross productivity may be relatively high, due to a high density of producers (high gross primary productivity) and consumers (high gross secondary productivity)
What is the energy loos like in a climax community
relatively high gross productivity is balanced by the large amounts of energy lost from the climax community system through respiration
What is the net productivity of a climax community
Approaching 0 this happens as the P:R ration approach’s 1. This ratio is reached when the biomass and energy is being produced by a system at the same rate it is being used
Is there one climax community
There is no one climax community, but rather a set of alternative stable states for a given ecosystem
- What the climax community eventually looks like depends on a large variety of factors, including climate, the local soil properties, and a range of random events that can occur over time (e.g. extreme weather events, human interventions)
What is the early stage of succession like
The GPP is low (due to the density of producers) but NPP as a percentage of GPP is relatively high, resulting in a an increase in overall biomass
What is the middle stage of succession like
GPP increases due to increased photosynthesis (as density of producers increases). As biomass continues to increase, NPP as a percentage of GPP reaches a peak and then starts to fall due to increase in respiration rates
What is the last stage of succession like
The productivity - respiration ratio approaches 1, as biomass and energy is being produced at the same rate it is being used by the system (through respiration and growth). At this point, there is no net productivity - the community has reached a stable state (the climax community)
What is population growth and regulation influenced by
A range of biotic and abiotic factors
What does density dependant factors include
Competition, predation, parasitism and disease
What happens the density depend and factors as population density increases
Factors become more significant, resulting in a decline in population growth rate. These ascot as a negative feedback mechanism leading the stability and regulation of populations
What does desinty independent factors include
factors include natural phenomena such as floods, fires, hurricanes, and droughts, as well as anthropogenic activities like pollution, deforestation, and climate change
How do density dependant factors affect growth rate
These factors affect the population growth rate irrespective of the population density, so their impact is similar across all populations regardless of their density
What is a r strategist
are characterised by having a high reproductive rate, small body size, early maturity, and short lifespan
What environments are r strategist species adapted to
unstable and unpredictable environments and tend to be found in pioneer communities
What is the growth rate and reproduction rate of r strategists
These species tend to have a high growth rate and reproduce quickly, producing large numbers of offspring with little investment in each
What is the survival rate of a r strategist species
They have a lower survival rate, but their high reproductive rate enables them to quickly recolonize and establish themselves after disturbances
What are some examples of r strategisits
Cockroaches, flies and small mammal species
How are populations of r strategists controlled
Density in dependant factors
How are k strategists species characterised
By having low reproductive rates, large body sizes, late maturity, and lingering lifespan
What are k strategists adapted to
Stable and predictable environments and tend to be found in climax communities
what is the growth rate and reproductive rate of a k species
Lower growth rates by invest more in each offspring, resulting in higher survival rates
What enviroment do they live in
They are better able to withstand disturbances, allowing them to persist in stable environments
What are some examples of k species
Large mammals
How can human activities affect the progression of succession
Human activities can divert the progression of succession to an alternative stable state by modifying the ecosystem through various activities,
What factors can alter the process of succession
Burning
Agriculture
Grazing pressure
Resource use
