2.4 - Biomes, Zonation And Succession Flashcards
Define biomes
are collections of ecosystems sharing similar climatic conditions which can be grouped into five major classes - aquatic, forest, grassland, desert and tundra. Each of these classes will have characteristic limiting factors, productivity and biodiversity.
What are the main factors governing the distribution of biomes
Insolation, precipitation and temperature are the main factors governing the distribution of biomes.
What is the tricellular model
The tricellular model of atmospheric circulation explains the distribution of precipitation and temperature influencing structure and relative productivity of different terrestrial biomes.
What is causing biome shifts
Climate change is altering the distribution of biomes and causing biome shifts.
Define zonation
Zonation refers to changes in community along an environmental gradient due to factors such as changes in altitude, latitude, tidal level or distance from shore (coverage by water).
Define succession
Succession is the process of change over time in an ecosystem involving pioneer, intermediate and climax communities.
What changes during succession
During succession the patterns of energy flow, gross and net productivity, diversity and mineral cycling change over time.
What leads to greater habitat diversity
Greater habitat diversity leads to greater species and genetic diversity.
What do r and k strategist species have
r and K strategist species have reproductive strategies that are better adapted to pioneer and climax communities respectively.
What is the energy like in the early stages of succession
early stages of succession, gross productivity is low due to the unfavourable 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.
What is the energy like in the later stages of succession
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 zero and the productivity:respiration (P:R] ratio approaches one.
What contributes to the stability of an ecosystem
In a complex ecosystem, the variety of nutrient and energy pathways contributes to its stability.
Is there one climax community
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 which can occur over time.
What one factor can divert the progression of succession
Human activity is one factor which can divert the progression of succession to an alternative stable state, by modifying the ecosystem, for example the use of fire in an ecosystem, 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.
Define biosphere
The biosphere is that part of the Earth inhabited by organisms. It extends from the upper part of the atmosphere down to the deepest parts of the oceans which support life.
State the 5 biomes
Aquatic - freshwater and marine
- Freshwater - swamp forests, lakes and ponds, streams and rivers, bogs
- Marine - rocky shore, mud flats, coral reel, mangrove swamp, continental shelf, deep ocean
Deserts - hot and cold
Forests - tropical, temperate and boreal (taiga)
Grassland - tropical or savanna and temperate
Tundra - Arctic and alpine.
What alters the types of biome
Each of these biomes will have characteristic limiting factors, productivity and biodiversity. Isolation, precipitation and temperature are the main factors governing the distribution of biomes.
What alters where biomes are located
The climate is the major factor that determines what grows where and so what lives where. The other important factor is the terrain or geography - slope, aspect and altitude. Climate is made up of general weather patterns, seasons, extremes of weather and other factors but two factors are most important - temperature and precipitation (rain and snowfall).
What affects the temperature from the poles to the equator
The temperature is hotter nearer the equator and generally gets cooler as we go towards the poles (increase latitude). This is due to the fact the suns rays hit the Earth at a more acute angle and so are spread over a greater surface area. You can see this effect if you shine a torch beam directly at an object which is flat in front of the torch or shining it at an angle.
How does latitude and altitude alter the climate
Latitude (distance north or south from the equator) and altitude (height above sea level) both influence climate and biomes. It generally gets colder as you increase latitude or increase altitude. So there is snow on Mt Kilimanjaro and the Himalayas and Andes and they have alpine or polar biomes even though they are at lower latitudes
How does oceans and winds distribute surplus heat
Ocean currents and winds distribute surplus heat energy at the equator towards the poles. Air moving horizontally at the surface of the Earth is called wind. Winds blow from high to low pressure areas. Winds cause the ocean currents. It is water that is responsible for transferring the heat. Water can exist in three states - solid (ice and snow), liquid (water) and gas (water vapour). As it changes from state to state it either gives out or takes in heat. This is its latent heat.
What happens to energy when water changes from solid to liquid
As water changes from solid to liquid (melts) to gas (evaporates), it takes in heat as more energy is needed to break the molecular bonds holding the molecules together.
What happens to energy as water changes from gas to liquid
As water changes from gas to liquid (condenses) to solid (freezes), it gives out heat to its surroundings. It is this change that distributes heat around the Earth. Water is the only substance that occurs naturally in the atmosphere that can exist in the three states within the normal climatic conditions on Earth.
What angle is the earth tilted
As well as orbiting around the Sun, the Earth rotates and is tilted at 23.5 degrees on its axis. It takes 365 days (and a quarter) for the Earth to go once round the Sun and this gives us a year and our seasons.
What are the most important abiotic factors that influence where biomes grow and are located and what must we use to compare them
Isolation, precipitation and temperature are the most important abiotic (physical) factors influencing biomes or what grows where. Increasing temperature causes increased evaporation so the relationship between precipitation and evaporation is also important. Plants may be short of water even if it rains or snows a lot if the water evaporates straight away (deserts) or is frozen as ice (tundra). So we must consider the precipitation to evaporation ratio
What happens when the precipitation is the same as evaporation
P/E ratio is approximately 1 when precipitation is about the same as evaporation; the soils tend to be rich and fertile.
What are some limiting factors affecting productivity in biomes
Different biomes have differing amounts of productivity due to limiting factors: raw materials or the energy source (light) for photosynthesis may be in short supply. Solar radiation and heat may be limited at the South Pole in winter, water in limited supply in a desert. All food webs depend on photosynthesis by green plants to provide the initial energy store so, if they cannot photosynthesize to their maximum capacity, other organisms will have a problem getting enough food.
Where is productivity greatest
Productivity is greater in low latitudes (nearer the equator), where temperatures are high all through the year, sunlight input is high and precipitation is also high.
Where is productivity lowest
Moving towards the poles, where temperatures and amount of sunlight decline, the rate at which plants can photosynthesize is lower, and thus both GPP (gross primary productivity) and NPP values are lower. In the terrestrial areas of the Arctic, Antarctic and adjacent regions (ie in high latitudes), low temperatures, permanently frozen ground (permafrost), long periods in winter when there is perpetual darkness, and low precipitation (cold air cannot hold as much moisture as warm air) all tend to cause a reduction in photosynthesis and lower productivity values.
In which ways are the climate changing
• Temperature increase of 1.5 to 4.5 °C by 2100 (according to the IPCC)
• Greater warming at higher latitudes
• More warming in winter than summer
• Some areas becoming drier, others wetter
• Stronger storms.
In which ways is climate change affecting biomes
• towards the poles where it is cooler
• higher up mountains where it is cooler - 500 m of altitude decreases temperature about 3 °C
• towards the equator where it is wetter.
What are 2 examples of biomes shifting
• in Africa in the Sahel region, woodlands are becoming savannas
• in the Arctic, tundra is becoming shrubland.
What factors are affecting the migration of animals to new locations due to climate change
Plants can only migrate very slowly as seeds are dispersed by wind or animals. But animals can migrate longer distances, eg albatrosses, wildebeest, whales.But there are obstacles to migration - natural ones like mountain ranges and seas and ones caused by human activities such as roads, agricultural fields and cities. Animals may not be able to cross these and could become extinct.
What are the hotspots which are thought to have a high turnover due to the turnover of species due to climate change
• The Himalayas - sometimes called the third pole - as species can move no higher than the land mass.
• Equatorial Eastern Africa - with a very drought-sensitive climate.
• The Mediterranean region.
• Madagascar.
• The North American Great Plains and Great Lakes.
What are 2 benefits to humans as biomes change and become vulnerable
• Drilling for oil under the Arctic Ocean is becoming possible with the decrease in sea ice.
• The North- West Passage for ships between the North Pole and North
America could become a trade route without icing up.
LOOK AT THE TRICELLULAR MODEL PAGE 105 IN YELLOW BOX
What is a tropical rainforest
Hot and wet areas with broadleaved evergreen forest.
Where are tropical rainforests
Within 5 degrees North and South of the equator.
What are climate and limiting factors in tropical rainforests
High rainfall 2000-5000 mm yr 1. High temperatures 26-28 °C and little seasonal variation.
High insolation as near equator. P and E are not limiting but rain washes nutrients out of the soil (leaching) so nutrients may be limiting plant growth.
What is the structure of a tropical rainforest
Amazingly high levels of biodiversity - many species and many individuals of each species. Plants compete for light and so grow tall to absorb it so there is a multi-storey profile to the forests with very tall emergent trees, a canopy of others, understorey of smaller trees and shrub layer under this - called stratification. Vines, climbers and orchids live on the larger trees and use them for support (epiphytes).
In primary forest (not logged by humans, so little light reaches the forest floor that few plants can live here. Nearly all the sunlight has been intercepted before it can reach the ground. Because there are so many plant species and a stratification of them, there are many niches and habitats for animals and large mammals can get enough food. Plants have shallow roots as most nutrients are near the surface so they have buttress roots to support them.
What is the net productivity in a tropical rainforest
Estimated to produce 40% of NPP of terrestrial ecosystems. Growing season all year round, fast rate of decomposition and respiration and photosynthesis.
Plants grow faster. But respiration is also high and for a large mature tree in the rainforest, all the glucose made in photosynthesis is used in respiration so there is no net gain. However, when rainforest plants are immature, their growth rates are huge and biomass gain very high. Rapid recycling of nutrients.
How is human activity influencing tropical rainforests
The problem is that more than 50% of the world’s human population lives in the tropics and subtropics and one in eight of us live in or near a tropical rainforest. With fewer humans, the forest could provide enough resources for the population but there are now too many exploiting the forest and it does not have time to recover. This is not sustainable. In addition, commercial logging of valuable timber, eg mahogany, and clear felling to convert the land to grazing cattle all destroy the forest.
What issues do tropical rainforests face from humans
Logging, clear-felling, conversion to grazing. Tropical rainforests are mostly in LEDs and have been exploited for economic development.
What are some examples of tropical rainforests
Amazon rainforest, congo in Africa, borneo rainforest
What is a temperate forest
Mild climate, deciduous forest
Where is a temperate forest found
Between 40° and 60° North and South of the equator.
What are some climate and limiting factors in a temperate forest
P > E. Rainfall is 500-1500 mm per year, colder in winter. Winters freezing in some (Eastern China and NE USA), milder in western Europe due to the Gulf Stream. Temp range - 30 °C to + 30 °C. Summers cool.
What is the structure if a temperate forest
Fewer species than tropical rainforests. For example in Britain, oaks, which can reach heights of
30-40 m, become the dominant species of the climax vegetation. Other trees, such as the elm, beech, sycamore, ash and chestnut, grow a little less high. Relatively few species and many woodlands are dominated by one species, eg beech. In USA there can be over thirty species per km?. Trees have a growing season of 6-8 months, may only grow by about 50 cm a year.
Woodlands show stratification. Beneath the canopy is a lower shrub layer varying between 5 m (holly, hazel and hawthorn) and 20 m (ash and birch). The forest floor, if the shrub layer is not too dense, is often covered in a thick undergrowth of brambles, grass, bracken and ferns. Many flowering plants (bluebells) bloom early in the year before the taller trees have developed their full foliage. Epiphytes, eg mistletoe, mosses, lichens and algae, grow on the branches. The forest floor has a reasonably thick leaf litter that is readily broken down. Rapid recycling of nutrients, although some are lost through leaching. The leaching of humus and nutrients and the mixing by biota produce a brown-coloured soil. Well-developed food chains in these forests with many autotrophs, herbivores (rabbits, deer and mice) and carnivores (foxes). Deciduous trees give way to coniferous towards polar latitudes and where there is an increase in either altitude or steepness of slope. P > E sufficiently to cause some leaching.
