What does a low standard deviation indicate
it indicates that the data collected has a narrow range and the points are closely grouped to the mean, therefore there is greater reliability
What does a high standard deviation indicate
A high standard deviation indicated that the data points have a larger range and are less well grouped, therefore there is a lower reliability
What does a T test do
- it compares two means, and it sees if you can agree with the null hypothesis or not
- if the T test bigger than the critical value then reject the null hypothesis
- if the t test is smaller than the critical value then accept the null hypothesis
how to work out the degree of freedom
sample size- number of means
Draw T test formula
Draw it
What is adaptation?
a characteristic that enhances survival in a habitat
What is a well adapted organism adapted to do?
- find enough food or photosynthesis well
- find enough water
- gather enough nutrients
- defend against predators and diseases
- survive the physical conditions of its environment for example temperature light
- respond to change in the environment
- have sufficient energy to allow for successful reproduction
What is Marram Grass
specialised plant that has adapted to living on sand dunes, it has to be able to take as much water in as possible therefore it is an xerophyte
What is anatomical adaptations
Any structural features that enhance the survival of the organism
Describe how Marram Grass is anatomically adapted?
- long roots - enables plant to reach water deep underground
- roots also spread out over a wide area - absorb a lot of water and helps stabilise the sand dunes in which the plant lives
- Curled leaves - this reduces surface area exposed to the wind and traps air inside against the lower epidermis therefore this increases the moisture that is there and creates a shallow water potential gradient
- Lower epidermis is covered in hairs - reduces air movement so that water vapour is retained closer to the lower epidermis
- Lower epidermis is folded to create pits where the stomata are - water vapour builds up in the pits this reduces the loss of water vapour as shallow water potential gradient created
- Low density of stomata - fewer stomata so less water lost
- Leaf in Waxy cuticle layer - reduces water evaporation from the cells of the leaf
What are behavioural adaptations?
The ways in which behaviour is modified for survival in the conditions that it lives in
Give some examples of behavioural adaptations
- when you touch an earthworm it curls up and withdraws into it burrow - this is to avoid being eaten
- marram grass responds to shortage of water by rolling up its leaf more tightly and closing the stomata this reduces the transpiration rate
- when covered by sand marram grass will grow more quickly to reach sunlight
What are physiological and biochemical adaptations
Any adaptation that ensures the correct functioning of cell processes, that enhance the survival of the organism
Give an example of physiological and biochemical adaptations
Yeast - Saccharomyces can respire sugars aerobically and anaerobically depending on how much oxygen is present
Explain Marram Grass physiological and biochemical adaptations
- the ability to roll its leaf due to the action of specialised hinge cells in the lower epidermis - these cells lose water when water is scarce and lose there turgidity - when water is available they become turgid and open leaves so they can gas exchange for photosynthesis
- The guard cells open and close the stomata, non-turgid cells close the stomata, turgid cells open the stomata
- Marram is not very salt tolerant but maintains a water potential that is lower than other plants - can survive in salty conditions
- The leaves contain many lignified cells that provide support when turgidity is lost keeping the plant upright when water is not available
What is a mole?
A borrowing animal that feeds on small animals in the soil
- Marsupial Moles live in Australia and have been evolving separately from placental moles for up to 100 million years
- still share similar characteristics and look very similar
What are the characteristics that Placental and Marsupial moles share
- cylindrical body
- small eyes
- strong front legs
- large claws on front legs
- short fur
- short tail
- nose with tough skin fro protection
Why do Placental and Marsupial moles look similar
- two unrelated species living in similar habitats evolve to have similar adaptations so therefore look very similar this is called convergent evolution
Describe how natural selection works
- Mutation creates alternative version of a gene
- this creates genetic variation between the individuals of a species
- once the variety exists then the environment selects those best adapted- when resources are scare those with the best variations will survive and have an advantage this is the selection pressure
- the individuals with the best characteristics will survive and reproduce
- they pass on their genes and the advantageous characteristic to the offspring
- the next generation will have a high proportion of individuals with the best adapted characteristics, over time the whole population will come to have a variety of the characteristic
Describe how some pesticides effect natural selection
An insecticide provides a very strong selection pressure to the insects
- the insects that are not immune to the insecticides will die but those who have some kind of resistance will survive, they can reproduce and pass on their characteristics therefore the resistance will spread rapidly through the population as only those who are resistant survive
Give examples of resistant to pesticides
- Pyrethroid insecticides are used to treat mosquito nets, the mosquito malarial parasites developed resistance to pyrethroids as they have produced an enzyme which breaks down the pyrethroid
- DDT is an insecticide which binds to the receptor of the plasma membrane of certain cells in insects - mutations have occurred which has altered the shape of the receptors of the plasma membrane therefore the DDT cannot bind to it
Why can insecticides be harmful
insects may be eaten by predators therefore the predators may have a large dose of the insecticide, this means the insecticide can move all the way down the food chain to humans and humans can receive a large dose of it
- DDT has been banned in many areas
How have microorganisms become resistant
- before selection there is variety levels of resistance
- variation is caused by mutations that create genetic variation within the species
- after selection the least resistance individuals are killed and the ones that remain are the resistant individuals
- reproduce and pass on the genes and characteristics to the next population
- next population contains a much higher proportion of resistant individuals
What leads to antibiotic resistance
- stop taking the antibiotics before you have finished them
- incorrect use of antibiotics
- prescribing multiple antibiotics which reduces the chances that some bacteria will survive
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Communicable diseases50
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Stuff Need To Know For The Exam18
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Biodiversity55
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Classification and Evolution55
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Biodiversity key terms16
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Communicable Diseases part 250
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Communicable diseases part 337
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Communicable diseases key terms37
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Classification and Evolution part 233
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classification and evolution definitions18
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conservation28
