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Core Biology Revision
Transcript of Core Biology Revision
Classification, Variation and Inheritance
Responses to a changing environment
Problems of, and solutions to a changing environment
How do we classify organisms?
Scientists classify organisms based on 7 groups.
A species is a group of organisms that can interbreed to produce fertile offspring
Variation is the difference between organisms and can be based on genetic factors or environmental factors.
Homeostasis is the maintenance of a stable internal environment.
Your body controls blood sugar levels, water content and temperature using negative feedback mechanisms.
The central nervous system is made up of the brain and spinal cord. The peripheral nervous system is all other nerves.
Hormones and diabetes
Hormones are chemical messengers that are carried in the blood.
Plant hormones and their uses
There are two different types of plant hormones you need to know about:
Auxins and gibberellins
Effects of drugs
A drug is a chemical substance that affects the central nervous system, causing changes in psychological behaviour and possible addiction.
Pathogens and infection
Infectious diseases are caused by pathogens.
Ethics and transplants
You should be able to discuss the ethical considerations of giving someone a transplant.
E.g giving an alcoholic a new liver or a smoker new lungs
+ they need the transplant and deserve the right to life
+ they should be entitled to the new organ as much as anyone else
- they did thedamage to themselves so dont deserve a new organ
- someone else might deserve it more
Influences on Life
The aim of this prezi is for you to revise all topics in core biology. There are videos, notes and spoken tutorials to help you.
The 5 kingdoms have specific features:
: multicellular, do not have a cell wall, feed heterotrophically
: multicellular, have a cell wall, contain chlorophyll, feed autotrophically
: multicellular, have cell walls, do not have chlorophyll, feed saprophytically
: unicellular, have no nucleus
: unicellular have a nucleus
Viruses are not classified into any of the 5 kingdoms because they are 'non-living'.
They cannot replicate on their own and need a host cell to survive and reproduce.
What is a chordate and how do we classify them?
A chordate is an organism that has a supporting rod running the length of its body (it has a backbone).
Chordate comes under the grouping of 'phylum'
We classify them in 3 main ways:
How do they absorb oxygen
? gills, lungs, skin.
How do they reproduce
? internal or external fertilisation, oviparous or viviparous (do they lay eggs or not?)
Their method of thermoregulation
. Poikilotherm or homeotherm?
How do scientists validate their evidence?
Scientists validate their evidence in many ways:
publishing in journals
Variation can be continuous or discontinuous.
Continuous variation is on a scale (e.g. height and weight)
Discontinuous variation is in categories (e.g. blood type and gender)
Causes of variation
Variation can be caused by genes (inherited from your parents) or by the environment
- blood group, eye colour
- weight, tattoos
Both types of variation
- height, skin colour, hair colour
Evolution is the gradual change in a species over time. The process of evolution occurs by natural selection.
Organisms with characteristics that help them adapt to an environment will survive. If they survive they are more likely to have offspring who they can pass on the genes to.
Over time, the species carries the genes for the adaptation and evolution has occured.
Watch the video to learn more about evolution, natural selection and speciation
Genes and inheritance
Genes are found in the nucleus of cells. Genes make DNA, DNA makes chromosomes.
Genes exist in different forms called alleles.
The gene for hair colour has the alleles; blonde, brown, black and red.
The gene for blood group has the alleles; A, B, O, AB
Looking at inheritance
Follow the link to have a go at the quiz.
You will need to draw punnett squares to work out your answers.
Watch the video to recap about family pedigree charts
Definitions of keywords
Dominant = only requires one copy for the trait to be seen
Recessive = requires two copies for the trait to be seen
Homozygous = two copies of the same allele (HH or hh)
Heterozygous = one copy of each allele, one dominant and one recessive (Hh)
Genotype = the alleles that a person has (bb)
Phenotype = the characteristic you see (blue eyes)
Gametes = sex cells (egg and sperm)
Vasoconstriction and Vasodilation
Vasoconstriction is where the blood vessel diameter gets smaller and less blood travels through the vessels. These blood vessels move away from the skin. This process helps the body to stay warm as the blood is not letting heat out through the skin.
Vasodilation is where the blood vessel diameter gets bigger and more blood travels through the vessels. The blood vessels move to the surface of the skin. This process helps to cool the body as it allows heat to radiate from the blood and out through the skin.
The body responds to a range of stimuli using the nerves throughout the body.
Stimulus -> detector -> sensory neurone -> relay neurone (in the spinal cord) -> motor neurone -> effector -> response
Watch the video to recap the main points for the topic of diabetes and how it effects the body
BMI (Body Mass Index)
You need to know how to calculate BMI.
If someone has a higher body mass index, they have an increased chance of developing type 2 diabetes
Osmoregulation - control of water content in the blood
Thermoregulation - control of the temperature of the body
Follow the link to read more information about how plant hormones work to aid growth.
How are plant hormones used commercially?
Plant hormones are used in many different ways for commercial benefits.
: auxin is used to help grow roots on plants. You can take a cutting from another plant and dip it in auxin powder and it will grow roots.
: auxin can be used as a weedkiller. It causes excessive growth of the plant. This means the plant cannot cope with the speed of growth and will die.
Control of ripening
: plant hormones can be used to control when crops ripen. This is why we can have fresh fruit and vegetables in the shops all year round.
: gibberellins control when seeds germinate so if we reduce the amount of gibberellin, we can delay germination so we can grow foods out of their normal season.
A tropism is growth in response to a particular stimulus
Phototropism is growth in response to light.
Positive phototropism is growth towards light.
Negative phototropism is growth away from light.
Geotropism (gravitropism) is growth in response to gravity.
Positive geotropism is growth towards gravity.
Negative geotropism is growth away from gravity.
What happens when blood sugar is too low?
What happens when the blood sugar is too high?
When the blood sugar decreases, this is detected by the body.
The pancreas releases glucagon.
The glucagon signals to the liver to break down glycogen into glucose.
The glucose is released back into the blood and raises the blood sugar levels.
When the blood sugar increases, this is detected by the body.
The pancreas releases insulin.
The insulin signals to the liver to collect glucose from the bood and store it as glycogen.
The glucose is removed from the blood and lowers the blood sugar levels.
The insulin can also signal to cells to take in more glucose which reduces the levels in the blood.
There are 4 different types of drugs that you need to be able to explain the effects for:
1. Painkillers (e.g. paracetamol, morphine, ibuprofen)
2. Hallucinogens (e.g. LSD, magic mushrooms)
3. Stimulants (e.g. caffeine, adrenaline)
4. Depressants (e.g. cannabis, alcohol)
Painkillers work by blocking nerve impulses.
This means the pain signal cannot be sent across a synapse.
Hallucinogens distort the sense perception.
This means people may hear, see, taste or feel things that are not really there.
Stimulants increase the speed of reactions (decrease reaction time).
They do this by speeding up the transmission of the signal at the synapse.
Depressants slow down the activity of the brain.
This makes reaction times slower (reaction times increase).
The effects of alcohol and smoking
Watch the video to recap your knowledge of how smoking and alcohol affect the body
Pathogens can be spread from one organism to another in many different ways:
- in water (like cholera bacterium)
- by food (like salmonella bacterium)
- through the air (like sneezing, coughing and flu)
- by contact (like athletes foot fungus)
- by body fluids (like HIV)
- by animal vectors (like housefly carrying dysentery and mosquito carrying malaria)
How do bacteria become resistant?
How does the body defend itself?
- stomach acid
- enzymes in tears
- cilia in lungs and nose
The Carbon Cycle
The Nitrogen Cycle
Antiseptics and Antibiotics
Parasites and mutualists
An antiseptic is a chemical used to destroy microorganisms outside the body
Antibiotics are chemicals used inside the body to kill or stop the growth of bacteria. They cannot work on viruses.
Antifungals are used to kill fungi
Interdependence is the relationship between living organisms
A parasite is an organism that lives on or off another organism and causes it harm.
A mutualist is a relationship where both organisms get a benefit out of the relationship
- live off animal blood by biting the skin.
- feed from human blood by biting the scalp
- live off food that the human eats by attaching themselves to the small intestine and absorbing nutrients
- lives off other trees and does not have roots of its own. It gets water and nutrients from the other tree.
A mutualistic relationship is a relationship between two organisms where they both get a benefit from it.
Oxpeckers and buffalo
: the oxpecker eats flies from the buffalo and this provides the bird with food.
Cleaner fish and sharks
: the fish eat algae from the shark and this provides the fish with food.
Nitrogen fixing bacteria and green plants
: the bacteria provide the plant with nitrates, the bacteria are protected by the plant by living in the root nodules.
Chemosynthetic bacteria and tubeworms
: the bacteria convert chemicals in the water to food for the worm, the worm protects the bacteria from the heat and predators.
The growing human population is causing increased amounts of pollution the atmosphere.
- More humans breathe out more carbon dioxide
- We burn more fossil fuels to produce energy which creates more pollution (Sulfur dioxide)
- We drive more cars so more pollution is released (Sulfur dioxide)
- We need more space for farming so cut down trees which decreases the amount of carbon dioxide being taken out of the atmosphere
- We use more fertilisers on fields which increases nitrate and phosphate pollution in rivers and lakes
Eutrophication is the process where water becomes polluted by nitrates and phosphates.
Excess fertilisers ared on fields and rain washes them into nearby rivers, streams and lakes.
The nitrates and phosphates in the fertilisers cause algae in the water to grow excessively and this blocks the sunlight from getting into the water.
Plants in the water die because they have no light to carry out photosynthesis.
Bacteria in the water grow excessively as they have lots of dead plants to feed on.
The bacteria use up the oxygen in the water.
Aquatic animals die because there is no oxygen in the water so they suffocate.
Indicators of pollution
We can use different living organisms to indicate the levels of pollution in a given area.
If you test a sample of water and find bloodworms or sludgeworms in it then the water is polluted.
If you test a sample of water and find stonefly or freshwater shrimps then the water is not polluted.
If you find lichens (on trees, rocks or buildings) or blackspot fungus (on roses) then it indicates that the air is polluted in that area.
And thats it!
This Prezi has covered all of your core biology topics so you should now feel confident with your topics.
Please use the OneNote and resources provided to work specifically on any other topics which you feel you need to focus on.
6 mark questions
Treatment of diabetes
- body does not produce enough insulin. Treated with careful monitoring of diet and injections of insulin.
- body becomes less sensitive to insulin. Treated with diet and exercise and sometimes medication to help the cells take in more glucose or the body to break down carbohydrates slower.