Posts Tagged ‘help’

  • Describe and evaluate methods for measuring changes in abiotic and biotic components of an ecosystem along an environmental gradient.
Ecological gradients are often found where two ecosystems meet. Biotic and abiotic factors change and form gradients in which then can be recorded. All parts of the gradient needs to be sampled, so a transect is used. The simplest one is when a line of tape is layed down across the area wanted to be measured then to take samples of all the organisms touching the tape. Many transects should be taken to obtain quantitative data. A belt transect is used for bigger samples.
  • Describe and evaluate methods for measuring changes in abiotic and biotic components of an ecosystem due to a specific human activity.
Chernobyl 1986, Russia:
Nuclear reactor blew up
  • design drawback
  • human errors due to poor supervision
The cause:
This caused an increase in thermal power which lead to more explosions. This contaminated soil, plants and animals.
Respond:
  • Fire fighters tried to turn it off, it took 5000 tonnes of sand, lead and clay.
  • The UN gave £75 million to make it safe and it was fixed by an international team ten years later.
  • People had to evacuate 30km away
  • The town was cleared of everything
  • 15cm of soil depth was removed
  • land washed away and dams were built
  • wall built around it
  • food was contaminated
  • Describe and evaluate the use of environmental impact assessment (EIA).
EIA: Environmental Impact Assessment
Process for identifying the likely consequence for the biophysical environment and for man’s health and welfare of implementing particular activities and for conveying information at a stage where it can materially affect the decision, to those for sanctioning the proposals. (long definition)
Purpose of the EIA:
Helps the decision making process by providing information about the consequences of the environment. Promotes sustainable development by identifying environmentally sound practice and migration measures for development.
Used for: 
Planning process that governments set out in law when large developments are considered. They provide a documented way of examining environmental impacts that can be used as evidence in the decision making process of any new development.
What developments used in the EIA:
  • Major new road networks
  • Airport/port developments
  • Building power stations
  • Building dams and reservoirs
  • Quarrying
  • Large scale housing projects.
Advertisements
  • Explain the concepts of limiting factors and carrying capacity in the context of population growth.
Carrying  capacity is the maximum number of organisms that an area or ecosystem can sustainably support over a long period of time.
There are however limiting factors including temperatures, water and nutrient availability. The main factors are temperature and water availability.
Limiting factors are factors that limit the distribution or numbers of a particular population. Limiting factors are environmental factors which slow down population growth.
Temperature:
There are many ways the temperature can affect species. For example some seeds only grow in extremely high temperatures as it enriches the soil with nutrients and kills competition. However some are damaged if they are too warm or too cold. Some are able to survive low temperature. Animals adapt to the hot/ cold temperature either by burrowing under the ground to avoid heat or having cold blood in the heat.
Water:
All plants/animals need water to survive, for plants have no water could cause the plant to not germinate or seeds to die. No water = Death.
  • Describe and explain S and J populations curves.
S-curve (Sigmoidal) : population growth curve that shows a rapid growth at the beginning then a slow down as the carrying capacity is reached.
J-curve:
A population curve which shows only exponential growth. It starts slow the becomes increasingly fast.
  • Describe the role of density-dependent and density-independent factors, and internal and external factors, in the regulation of populations.
Density-dependent factors:
Factors that lower the birth rate or raise the death rate as a population grows in size. They are negative feedback mechanisms leading to the stability or regulation of the population.
When prey increases so does the predator, but when this occurs the prey decreases and then again the predators decrease too causing the prey to increase again.
Density-independent factors:
Factors that affect a population irrespective of population density notably environmental change. Abiotic factors are density-independent factors, the most important ones are the extremes of weather (droughts, fires and hurricane) and long-term climate change.
These factors have an impact that can increase the death rate and reduce the birth rate, it all depends on how severe the event was.
Factors which regulate population size can be divided into either INTERNAL or EXTERNAL.
Internal:  fertility rates, territory sizes
External: predation, pressure, parasitism
The major cause of population regulation are in the environments, these can be physical or biological.
The physical class of environmental factors are water availability, nutrient availability anf so on.
Biological factors include predators, and competition.
Ways humans can cause population growth:
  • increase available resources
  • reduce competition
  • reduce pressure from predators
  • introduce animals to new areas
Ways to decline population:
  • change environment, cause habitat disruption
  • change the biological environment by introducing new species
  • cause secondary extinctions
  • overkill
  • Describe the principles associated with survivorship curves including, K and r strategists.
Survivorship curves and r and k strategists:
K-strategists are slow growing and produce few, large offspring that mature slowly.
R-strategists, slow and mature quickly and produce many, small offspring.
K= carrying capacity
R= growth rate
K-strategist:
  • low reproductivity
  • large investment in parental care
  • late maturity/longer living
  • slow growth
  • larger size
  • require stable environment
R-straegists:
  • high reproductivity
  • short life
  • low investment in parental care
  • early maturity
  • rapid growth
  • small organisms
  • highly adaptable
  • large number of few species
Survivorship rates:
What influences survivorship rates:
  • competition for resources
  • adverse environmental conditions
  • predator-prey relationships
Example of 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 survives lives very long life turtles/ oysters. (r-strategists)
  • Describe the concept and processes of succession in a named habitat.
Succession: Change in the community structure of a particular area over time.
Primary succession: colonization of newly created land by organisms (rock).
Secondary succession: occurs in places where a previous community has been destroyed. (forest/fire) It is faster than primary succession because of the presence of soil and a seed bank.
Pioneer= earliest community of the succession.
Climax community= the last and final community.
The change from pioneer to climax is called a sere.
Succession is the process of change over time in a community changes in the community of organisms frequently cause changes in the physical environment that allow another community to become established and replace the former through competition. They get more complex at the end.
Zonation:
The arrangement or patterning of plant communities or ecosystems into bands in response to change, over a distance, in some environmental factor.
The main biomes display zonation with altitude on a mountain, or around the edge of a pond in relation to soil moisture.
  • Explain the changes in energy flow, gross and net productivity, diversity and mineral cycling in different stage of succession. 
GP, NP and diversity will change over time as a ecosystem goes through succession. GP is low in early stages then increases as soils become more structured. As food webs become more structured NPP and diversity stabilize as the ecosystem reach climax population.
  • Describe factors affecting the nature of climax communities. 
Climax community:
  • greater biomass
  • higher levels of species diversity
  • more favourable soil condition
  • better soil structure
  • lower pH
  • taller and longer living plant species
  • more k-strategies or fewer r-strategist
  • greater habitat diversity
  • steady state equilibrium
Climate and edaphic factors determine the nature of a climax community. Human factors frequently affect this process through, for example; fire, agricultures, grazing and/or habitat destruction.
  • Explain the role of producers, consumers and decomposers in the ecosystem.
Producer: can make their own food, as they use sunlight to make food and are called  the basis of every ecosystem which helps the rest of the species through input of energy and new biomass. This all happens through photosynthesis which is the process when the producer uses the sun for energy.
Consumer: feed on other organisms, they do not contain photosynthesis pigments so they cannot make their own food. They have to get energy, minerals and nutrients by eating other organisms. This makes the heterotrophs. Herbivores feed on autotrophs, carnivores on other heterotrophs and omnivores on both.
Decomposer: get their food from the breakdown of a dead organism matter. They break down tissue and release nutrients for absorption by other producers. Decomposers also improve the nutrient capacity in the soil by breaking down the organic material.
  • Describe photosynthesis and respiration in terms of inputs, outputs and energy transformations.
Photosynthesis: needs carbon dioxide, water, chlorofyll and certain visible wave lengths of light to produce organic matter and oxygen.
  • inputs: sunlight as energy resource, carbon dioxide and water
  • processes: chlorofyll traps sunlight; energy is used to split water molecules; hydrogen from water is combined with carbon dioxide to produce glucose.
  • outputs: glucose used as an energy source for the plant and as a building block for other organic molecules; oxygen is released to the atmosphere through stomata.
  • transformations: light energy is transformed to store chemical energy.
Respiration: needs organic matter and oxygen to produce carbon dioxide and water.
  • inputs: glucose and oxygen
  • processes: oxidation processes inside cells
  • outputs: release of energy for work and heat
  • transformations: stored chemical energy to kinetic energy and heat
  • Describe and explain the transfer and transformation of energy as it flows through an ecosystem.
Not all solar radiation ends up being stored as biomass. Losses include_
  • reflection from leaves
  • light not hitting chloroplasts
  • light of the wrong wavelengths (not absorbed by chloroplast pigments)
  • transmission of light through the leaf
  • inefficiency of photosynthesis
In this diagram we can see the energy flow through an ecosystem.
  • Describe and explain transfer and transformation of materials such as they cycle within an ecosystem.
The Carbon Cycle:
The Hydrological cycle:

The nitrogen cycle:
¨
  • Define the terms gross productivity, net productivity, primary productivity, and secondary productivity.
*Productivity is production per unit time.
Primary productivity is the gain by producers (autotrophs) in energy or biomass per unit area per unit time. It is when solar energy is converted, it depends on the amount of sunlight the ability of the producers to use energy to synthesize organic compounds and the availability of other things needed for growth, like minerals and nutrients.
Primary production is highest were conditions for growth are optimal, where there are high levels of insolation, good water supply, warm temperatures and high nutrient levels.
You can then divide primary productivity into gross and net profits.
*GROSS is the income
*NET is the incomes minus costs
Secondary productivity depends on the amount of food there is and the efficiency of the consumers turning this into new biomass. Unlike the primary productivity net productivity involves feeding or absorption.
Gross productivity (GP): The total gain in energy or biomass per unit area per unit time.
Net productivity (NP): The gain of energy or biomass per unit area per unit time remaining after allowing for respiratory losses. It is the energy left for the next trophic level to consume.
  • Define the terms and calculate the values of both gross primary productivity and net primary productivity from given data.
Gross primary productivity (GPP): is gained through photosynthesis in primary producers.
Net primary productivity (NPP): is the gain by prodicers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses. (Available for consumers in ecosystem)
Productivity calculation:
Primary productivity:

where R = energy used in respiration
NPP = GPP – R
  • Define the terms and calculate the values of both gross secondary productivity and net secondary productivity from given data.
Gross secondary productivity(GSP): is gained through absorption in consumers.
Net secondary productivity(NSP): The gain by consumers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses.
Secondary productivity:
NSP = GSP – R
GSP = food eaten – faecal loss
where R = respiratory loss
  • Define the term biome.
Biome:
A collection of ecosystems sharing similar climatic conditions, like tundra, tropical rainforest and desert. A biome has distinctive abiotic factors and species which distinguish it from other biomes. Water, insolation and temperature are the climate controls important when understanding how biomes are structured, how they function and where they are found round the world. Biomes usually cross national boundaries and do not stop at a border.
  • Explain the distribution, structure and relative productivity of tropical rainforests, deserts, tundra and any other biome.
It is possible to group the biomes into 6 categories with sub-categories in each one:
  • freshwater
  • marine
  • desert
  • forest
  • grassland
  • tundra
In IB however 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.
In this picture you can see where each biome is located.
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
Deserts:
  • cover 20-30 percent of the land surface
  • dry air
  • high temperatures (45-49 C in day)
  • low precipitation (250 mm yr-1)
  • low rates of photosynthesis
  • low NPP rates
  • vegetation scarce
  • soil rich in nutrients and can support plant that can survive there
Tundra:
  • 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 soil are limited
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
  • mild climate, lower average temperature / lower rainfall

  • Construct simple keys and use published keys for the identification of organisms.

Keys called dichotomous keys are used to identify species, the key is written so that the identification is done in steps. At each step two options are given based on different possible characteristics of the organism you are looking at.  You go through all the steps until the name of the species is discovered. This is an example of a dichotomous key that divides 4 types of egg-laying species:

For the exams you need to have at least eight species in the key you construct. This can also be shown graphically:

  • Describe and evaluate methods for estimating abundance of organisms.
It is impossible for you to study every organism in an ecosystem, so limitations must be put on how many plants and animals you study. There are trapping methods which help obtain more samples, like:
  • pitfall traps
  • small mammal traps
  • light traps
  • tullgren funnels
You can either count them all or using percentage cover of an organism in a selected area or by using the Lincoln index and calculating the abundance.
Lincoln index:
This method allows you to estimate the total population size of an animal in your study area. This method includes collecting a sample from a population, then marking them like painting or attaching something to the animal, releasing them back into the wild, then resampling some time later and counting how many marked individuals you find in the second capture. IT is important to take into consideration that the marking methods are not harmful to the animal and clear so that they do not become easy targets for prey.
This method is also known as capture-release-mark-release-recapture techniques because of the processes involved. If all the marked animals are recaptured that is assumed to be the total population size of that species. whereas if half of the species is captured it is estimated to be twice as much as the first sample. The formula used to calculate population size:
N= total population size of animals in the study site
n1= number of animals captured of first day
n2= number of animals recaptured
m= number of marked animals recaptured on the second day
N= (n1 x n2) / m
Quadrats:
Quadrats are used to measure the percentage cover of a certain species. Ecologists want to find out how many organisms are living in a specific area, however they cannot count them all so they make a sample count. Percentage cover is the area within the quadrat being used by one particular species.
Percentage cover is worked out for each species present. Dividing the quadrat into a 10×10 grid helps to estimate percentage cover.
Sample methods must allow for the collection of that is scientifically representative and appropriate, and allow the collection of data on all species present. Results can be used to compare ecosystems.
Percentage frequency is the percentage of the total quadrat number that the species was present in.
  • Describe and evaluate methods for estimating the biomass of trophic levels in a community.
*Biomass:  the mass of organic material in organisms or ecosystems, usually per unit area. Biomass is calculated to indicate the total energy within in a living being or trophic  level. The greater the mass of the living material the greater the amount of energy present. Biomass is taken as the mass of an organism minus water content, like dry weight biomass. Water is not included in biomass measurements because the amount varies from organisms to organism, it does not contain energy and is not organic.
To obtain the samples, the biological material is dried to constant weight. It is then weighed. The specimens are then heated in a  oven which is not hot enough to burn the tissue and left for a certain amount of time. Biomass is usually measured per unit area so that comparisons can be made between the trophic levels present.
  • Define the term biodiversity.
Diversity is often considered as a function of two components: the number of different species and the relative numbers of individuals of each species. This is different from species richness, which refers only to the number of species in a sample area.
  • Apply Simpson’s diversity index and outline its significance.
There are many ways of quantifying diversity, one of the ways is using the Simpson’s diversity index:
D= diversity index
N= total number of organisms of all species found
n= number of individuals of a particular species
E= sum of
D= (N(N-1)) / (En(n-1))
*It is not important to remember the whole formula, but good to know the meaning of the symbols.
D is a measure of species richness. A high value of D suggests a stable and ancient site, and a low value of D could suggests pollution, recent colonization or agricultural management. The index is normally used in studies of vegetation but can also be applied to comparisons of animal diversity.
  • List the significant abiotic (physical) factors of an ecosystem.

Ecosystems can be divided into 3 types:

  • Marine: the sea, salt marshes mangroves are all characterized by the salt content.
  • Freshwater: rivers, lakes and wetlands.
  • Terrestrial: land-based.

Each ecosystem has its on abiotic factors:

Marine:

  • salinity
  • pH
  • temperature
  • dissolved oxygen
  • wave action

Freshwater:

  • turbidity
  • flow velocity
  • pH
  • temperature
  • dissolved oxygen

Terrestrial:

  • temperature
  • light intensity
  • particle size
  • slope/aspect
  • soil moisture
  • drainage
  • mineral content
  • Describe  and evaluate methods  for measuring at least three abiotic (physical) factors within an ecosystem.

Abiotic factors that can be measured within an ecosystem include the following:

Marine:

  • salinity: this can be measured  using electrical conductivity ( with a datalogger) or by the density of the water (water with high salt content is more denser than low-salt water).
  • pH: this can be measured using a pH meter, or datalogging pH probe. Indicator solution may also be used.
  • temperature: ordinary thermometers are too fragile to use for fieldwork, and are hard to read. An electric thermometer allows temperature to be measured  in depth.
  • dissolved oxygen: a meter with oxygen-sensitive electrodes connected that measures dissolved oxygen. One should be careful as doing things wrong may contaminate the air.
  • wave action: this is measured by using a dynomometer which measures the force in waves.

Freshwater:

  • turbidity: can be measured using a Secchi disc, nephlometer or turbidimeter.
  • flow velocity: can be measured by timing how long it takes a floating object to travel a certain distance or by using a flow-meter.
  • temperature: ordinary thermometers are too fragile to use for fieldwork, and are hard to read. An electric thermometer allows temperature to be measured  in depth.
  • dissolved oxygen: a meter with oxygen-sensitive electrodes connected that measures dissolved oxygen. One should be careful as doing things wrong may contaminate the air.

Terrestrial:

  • temperature: ordinary thermometers are too fragile to use for fieldwork, and are hard to read. An electric thermometer allows temperature to be measured  in depth.
  • light intensity: is measured using a light-meter.
  • wind speed: a Beufort-scale is used to measure wind speed and precise measurements can be made with a digital anemometer.
  • particle size: this determines the drainage and water-holding capacity and is measured by using a series of sieves.
  • slope: this is measured using a clinometer and using a compass.
  • soil moisture: by weighing the samples then heating them it shows the amount of water that has evaporated and the moisture levels.
  • mineral content: the loss on the ignition test can determine mineral content. The samples are heated for several hours to let volatile substances to escape.
Abiotic data can be collected using instruments that avoid issues of objectivity as they directly measure quantitative data. Instruments allow us to record data that would otherwise be beyond the limit of our perception.
  • Distinguish between biotic and abiotic (physical) components of an ecosystem.

*Biotic: refers to the living components of an ecosystem. (the community)

*Abiotic: refers to the non-living factors of an ecosystem. (the environment)

Ecosystems are made up of living and non-living components. The living part of the environment consists of the organic part of the ecosystem; animals, plants, algae, fungi and bacteria. These are called biotic components. The non-living part of the environment is made up of physical components such as; air, light, water, temperature, soil, minerals and climatic atmosphere. These are called abiotic components. These two components work together to sustain the environment.

  • Define the term trophic level.

Trophic level refers to the feeding level within a food chain. It is the position that an organism occupies in a food chain, or a group of organisms in a community that occupy the same position in food chains.

  • Trophic level 1 – producer
  • Trophic level 2 – herbivore (primary consumers)
  • Trophic level 3 – carnivore (secondary consumers)
  • Trophic level 4 – carnivore (tertiary consumer)
    • Identify and explain trophic levels in food chains and food webs selected from the local environment.

    *Producer: The organism in the ecosystem that converts abiotic components into living matter, they help the ecosystem by producing new biological matter.

    *Consumer: These organisms cannot produce their own food, so they eat other organisms to get the energy and matter they need.

    * Decomposer: Feed on dead biomass which is created by the ecosystem.

    *Herbivore: Only feed on producers.

    *Carnivore: Feed on all organisms including producers and consumers.

    *Top carnivore: This organism can not be eaten by any other organism.

    Sun: Provides the abiotic matter to the grass

    Grass: Producer and autotroph, provide food for the deer.

    Deer: The primary consumer and herbivore of the grass.

    Wolf: The secondary consumer/Top consumer and carnivore, feeds on the deer and cannot be eaten by any other organism.

    Ecosystems contain many interconnected food chains that form food webs. Food chains always begin with the producers (usually photosynthetic organisms), followed by primary consumers (herbivores), secondary consumers (omnivores or carnivores) and then higher consumers (tertiary, top). Decomposers feed at every level of the food chain.

    Diagrams of food webs can be used to estimate the knock-on effects of changes to the ecosystem.

    Biomass and energy decrease at each trophic level so there is a limit in how much trophic levels can be supported in a ecosystem. Energy is lost as heat at each stage of the food chain, on only energy stored in biomass is passed on to the next trophic level. After 4 or 5 trophic levels there is not enough energy to support another stage.

    Local example: (Lake in Sweden)

    Producer: Freshwater shrimp

    Primary consumer: Bleak

    Secondary consumer: Perch

    Secondary consumer: Northen Pike

    Top consumer: Osprey

    • Explain the principles of pyramids of numbers, pyramids of biomass, and pyramids of productivity, and construct such pyramids from given data.

    Pyramids are graphical models showing the quantitative differences between the trophic levels of an ecosystem. There are three types:

    • Pyramids of numbers: This records the number of individuals in each trophic level.

    • Pyramid of biomass: This represents the biological mass of the standing stock at each trophic level at a particular point in time. Biomass should also be measured in units of energy, such as J m-2. They can show greater quantities at higher trophic levels because they represent the biomass present at a given time. Both pyramids of numbers and biomass represent storages.

    • Pyramid of productivity: This shows the flow of energy through each trophic level. Measured in units of flow gm-2 yr-1 or Jm-2 yr.

    In accordance with the second law of thermodynamics, there is a tendency for numbers and quantities of biomass and energy to decrease along food chains; therefore pyramids become narrower as one ascends.

    • Discuss how the pyramid structure affects the functioning of an ecosystem.

    This Youtube clip explains the interactions in food chains and the vulnerability of the top carnivores.

    • Define the term species, population, habitat, niche, community and ecosystem with reference to local examples.

    *Species: A group of of organisms that interbreed and produce fertile offspring. If two species breed together they create a hybrid, this cannot produce viable gametes and is sterile.

    *Population: A group of the same species living in the same area at the same time, and can interbreed.

    *Habitat: The environment in which a species normally lives.

    *Niche: Where and how a species lives. A species share of a habitat and the resources in it.

    *Community: A group of populations living and interacting with each other in a common habitat.

    *Ecosystem: A community of inter-independent organisms and the physical environment they inhabit.

    • Describe and explain population interactions using examples of named species.

    Ecosystems contain many interactions between the populations, the interactions are varied and can be divided into; competition, predation, mutualism and parasitism.

    *Competition: A common demand by two or more organisms upon a limited supply of a resource; for example, food, water, light, space, mates, nesting sites. It may be intraspecific or interspecific.

    *Parasitism: A relationship between two species in which one species (the parasite) lives in or on another (the host), gaining all or much (in the case of the partial parasite) of its food from it.

    *Mutualism: A relationship between individuals of two or more species in which all benefit and non suffer.

    *Predation: This is when on animal or plant hunts and eats another animal.


    Here are 3 Youtube links about Interspecific interactions.