BIOLOGY REVISION

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Nervous system and reflex actions

 

Reflect actions happen very quickly. Most of them are meant to protect the body.

For example: your eyes are delicate and important, so you have a blink reflex if something comes near them.

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Nervous system and reflex actions

Reflexes happen quickly because the impulses are not rouuted via the brain, and they are in voluntary. 

CNS: the brain or spinal chord

Synapses: the gaps between neurons

Electrical  impulses: how signals tavel within a nerve cell

Neurotransmitters: the chemicals that carry signal across synapses 

Axon: the long aprt of the neuron that carries the signal

Dendrite: a branch on a neuron that connectsto an adjacent neuron

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Infectious Diseases

A microbe is a single-celled organism that is too small to see with the naked eye. in the right conditions, microbes can reproduce rapidly forming visable colonies on a Petri Dish.

There are 3 main types of microbe: Bacteria, Fungi and Viruses.

Bacteria are like a cell, but without a proper nucleus. They can have a tail, called a flagellum to move around.

Viruses are smaller than other types of microbes. They can be strange geometric shapes and can only live inside another living cell.

Athlete's foot is an example of Fungi

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Defence

A= Salty liquid is antiseptic

B= Wax traps microbes

C= A physical barrier to microbes

D= Mucus traps microbes

E= Sweat and oils discourage microbe growth

F= Acid kills most microbes                                    

                                                                                                    

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Infectious Diseases Key Terms

Pathogen: general term for harmful microbes 

Immunity: defences against that particular disease 

Antibodies: markers produced by some white blood cells to tag invaders

Engulf and Digest: what some white blood cells do to invading pathogens

Toxins: waste products produced by pathogens. This is what makes you feel ill

Vaccine: a weak or dead form of a disease: not enough to make you ill, but enough to get your                   immune system to make antibodies against it 

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Antibiotics

Antibiotics are used to fightinfections inside the body. However they are little use against viruses, because they are inside the body's cells.

                                                

Because of variation within any population, some of the bacteria are likely to become resistant to an antibiotic. If you stop taking the antiboitics as soon as you stop feeling ill, and therefore not taking the full course, these bacteria will be able to multiply and make you ill again.

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Controlling conditions

It is vital for our health that conditions in the body are kept constant.

Our core body temperature must be kept close to 37°C. This is the optimum temperature for most enzymes to work in. If the core temperature is colder than that then the rate of the chemical reaction falls. If the core temperature is hotter, then the enzymes become denatured.

Keeping internal conditions constant, called homeostatis, is an example of negative feedback; the system taking action to cancel out the effects of any changes.                                                                                                                                        

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Controlling conditions

The kidneys...control the amount of water and ions lost in the urine.

The hypothalamus...is the thermoregulatory centre of the brain.

Blood sugar...provides cells with a supply of energy.

Carbon Dioxide...is removed by the lungs.

                                                                              

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Controlling conditions

The skin...is an effector for controlling the amount of heat lost by the body.

Sweating...removes heat by evaporation.

Hypothermia...is when the core body temperature falls too much.

Hyperthermia...is when the core body tempertaure rises too much.                                                                                                                          

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Regulating Conditions

There are 2 main ways that regulate conditions in our bodies: the nervous system and the endocrine system.

This system uses impulses travelling along neurones: NERVOUS SYSTEM

This system uses hormones: ENDOCRINE SYSTEM

This system works fastest: NERVOUS SYSTEM

The pituitary gland controls ovulation: ENDOCRINE SYSTEM

The pancreas regulates glucose levels: NERVOUS SYSTEM                                                                                         

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Controlling Heat Loss

The skin has several mechanisms for controlling heat loss.

                 

If we get too hot, the sweat glands produce more water. The capillaries (carrying the blood near the skin surface) dilate, increasing the blood flow and making the skin appear redder. The hairs lie down to trap less air.

If we get too cold, sweat isn't produced, the capillaries constrict, and the hairs stand up to trap more air to form an insulating layer.

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Effect of Exercise

Muscle cells contract when an electrical impulse from a nerve is applied. This means that muscles can pull, but not push, which is why many of them are arranged in pairs.

                                   

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Effect of Exercise

Muscle cells are mainly composed of protien.

The cells contain many mitochondria to supply the energy required to move. These release energy using aerobic respiration

                                               .

The equation for this is:

GLUCOSE + OXYGEN   Right arrow (http://officeimg.vo.msecnd.net/en-gb/files/120/764/ZA006052154.gif)  CARBON DIOXIDE + WATER                             

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Exercise

During exercise, muscles need more of Glucose and Oxygen. 

Heat and Carbon Dioxide are taken away from the muscle during exercise

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Exercise

What happens to your body during exercise?

Because the uscles need more oxygen, your heart rate, breathing rate and the depth of your breathing will all increase.

Also, the arteries supplying the blood to the muscles will dilate, increasing the blood flow.

                    

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Exercise

If someone is fit, how is their body different?

The size of their lungs is increased.

the resting heart rate is decreased.

The breathing rate during exercise is deacreased.

In someone exceptionally fit, such as a trained athlete, the size of their heart is increased.

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Exercise Graph

2 people of the same age ran alongside eachother to catch a bus. The graph below shows their heart rate directly after this exercise. 

                       

The blue line represents the fit person, and the red line represents the unfit person.

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Exercise Graph

How long did it take each person's heart rate to return totheir resting rate?

                         

It took the fit person's heart 5 minutes to return toits resting rate.

It took the unfit person's heart 8 minutes to return to its resting rate. 

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Summary of Exercise

                     

Muscles need an increased supply of oxygen and glucose during exercise. 

If you are fit, your resting heart rate is lower and it returns to normal more quickly after exercise.

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Drug abuse

What is a drug? 

A drug is a substance that affects the way your ming and body works.

                 

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Drug abuse

      

THESE ARE ALL DRUGS.

Most drugs can classified as Stimulants, Depressants or Hallucinogens.

 Stimulants increase alterness , attention and energy, elevate blood pressure and increase heart                      rate and respiration.

Depressants slow down brain functionality.

Hallucinogens alter perceptual functions.


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Drug abuse

Stimulant: 

Depressant:   

Hallucinogen:  

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Alcohol

Alcohol is quickly absorbed into the bloodstream from the stomach. Even smal doses will slow down your reations. Alcohol is broken down by your liver which can be damaged overtime by having to do this too much.

Alcohol is also a carbohydrate so it contains energy, which means that excessive consumption can leadto obesity.

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Nicotine

Tobacco smoke contains a drug called Nicotine to which users can become addicted. 

What is in cigarette smoke? 

= Arsenic, Carcinogens (cancer causing substances), Hydrogencyanide, Carbon dioxide, Tar, Carbon monoxide.

                                                                      

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Drug abuse

Substances that can cause cancer are called Carcinogens. There are many of these in cigarette smoke.

Carbon monoxide is a taxic gas that is absorbed by red blood cells. This prevents them fromtransporting oxygen to the parts of your body that need it.

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Healthy Eating

We need dome fat and carbohydrates (including sugar) in our diet in order to remain healthy. It is important not to eat too much of these however. Having a balanced dietmeans eating the right amounts of different types of nutrients. 

Ways to improve your diet are things such as: not skipping breakfast, cutting down on salt etc...                                        

                                         

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Healthy Eating Key Terms

Deficiency diseases: what can happen if you don't get the right nutrients.

Energy: Carbohydrates and fats are high in this.

Protein: meat, fish and nuts are high in this.

Saturated fat: too much of this in your diet can raise your cholesterol.

Salt: too much of this in your diet can raise your blood pressure.

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Food Pyramid

                      

 

                      

                        we need only a little of B, but alot of D, and E!

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Menstrual Cycle and Fertility Control

The menstrual cycle usually lasts for about 28 days. The period usually lasts for about 5 days.

The medical name for a period is Menstruation.

The eggs (ova) are released from the ovaries.

The cycle is contolled by hormones made by the pituitary gland(s) and the ovaries.                                                        

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Menstrual Cycle

                                   

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Menstrual Cycle

                                   

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Menstrual Cycle

The menstual cycle is controlled by 4 hormones.

Progesterone: made in the ovaries. Maintains lining of uterus.

Oestrogen: Made in the ovaries. Causes uterus lining to thicken, and stimulates the production of                   LH.

LH (Lutienising hormone): Made in the pituitary gland. Stimulates release of egg.

FSH (Follicle Stimulating Hormone): Made in the pituitary gland. Stimulates eggs to mature.                                                              Stimulates the ovariesto produce oestrogen.

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Fertility Control- Contraception

The contraceptive pill contains hormones thatinterfere with the menstrual cycle. 

One common type contains oestrogen, which may seem strange because it stimulates the productoin of LH, which causes eggs to be released.

However, if levels of oestrogen are permanently high, it inhibuts the production of FSH, so eggsdon't mature and don't get released. 

                                    

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Fertility Treatment

FSH can be  given as a fertility drug, in order to stimulate the eggs to mature. Alternatively, other drugs can be used depending on the reason for infertility.

                               

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Adaptation For Survival

 ARCTIC HARE:

* Camouflage

* Eyes on side of head to spot predators

*Less heat loss from ears

*Thicker fur to minimise heat loss

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Adaptation For Survival

HARE:

*Larger ears

*More heat loss from ears

*Camouflage

*Eyes on side of head to spot predators

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Adaptation For Survival

To minimise heat loss, animals in cold climates need a ratio of small surface area to thier volume. Thistends to mean that they are large animals with small ears.                                                                                                                                  

Ina hot, dry climate, plants andanimals are adapted to minimise water loss. 

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Cactus Adaptations

How is a cactus adapted to survive in desert conditions?

1) Ribbed surface to allow expansion when rain arrives and is absorbed by the roots.

2) Chlorophyll in stem for photosyhthesis.


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Competition in animals and plants

                  

What do plants compete for?

Nutrients from the soil, Light, Water from the soil.

What do animals compete for?

Food, Status, Territory, Mates.

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Evolution

The way that living things change slowlyover time is called Evolution. If this goes on for long enough it can give rise to new species.

Back in the 1800's, scientists had suspected this for some time. The work of Charles Darwin revealed that evolution works because of natural selection, which has since been described as ''survival of the fittest''

                                

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Evolution - Fossils

Much of our evidence for evolution comes from the 'fossil record' - fossils that we have found and dated, and from which we have pieced together fragments of the history of life on earth. 

How where fossils formed?

1) An ammonite dies and become buried in sediments

2) More and more sediment biulds up. There ust be no oxygen present.

3) The layers above compress the sediment. The body has decayed, but the shell remains. 

4) Eventually, the shell decays, leaving a cavity in the rocks as it forms.

5) Other minerals fill the cavity.                                                                                                                                                                               

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Evolution - How it works

Within species, some individuals will be taller, shorter, faster, slower or different in other ways. This is called variation and is a consequence of sexual reproduction and mutations - random erros when genes are copied or passed on. Most of these differences will have no effect, but some of them may give the organism an advantage when competing for food, mates or territory.

Darwin realised that variation within a species would affect the survival chances of individuals, leading to "natural selection". 

                                           

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Natural Selection- Darwin's Big Idea

Because of variation within a species, some individuals will be better suited to their environment than others.

This gives them an advantage and makes them more likely to survive long enough to breed.

The characteristics that gave them the advantage will be passed on to their offspring who will also be more likely to survive. 

Given enough time, most of these species will be descended from those 'winners'.

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Variation

Variation refers to the differences between individuals in a species. 

Species: a group of organisms that can breed with each other to produce fertile offspring.

Nucleus: where the genetic information is found in a cell.

Clone: an organism that is genetically identical to its parent.

Gametes: Sex cells, such as sperm and egg.

                   

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Variation

Largest:  Nucleus (each cell has one of these)

               Chromosome (Humans have 46 of these in each cell)

               Gene (a section on a chromosome. It specificies one of your characteristics) 

Smallest: Base Pairs  (a sequence of these makes a gene)(http://www.angelo.edu/faculty/mdixon/HumanBiology/cellgene.jpg)

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Variation

Variation occurs because there are sometimes erros when cells divide and genes are copied and because sexual reproduction creates many different combinations of genes in the population. Chromosomes are long molecules of DNA, the shapes is a double helix. It looks like a ladder that has been twisted. A gene is a section on a chromosome. It is a sequence of base pairs which are like the rungs on a ladders. Humans have 46 chromosomes in each cell, in the form of 23 pairs.Each pair has 1 chromosome from the mum, and the 1 from the dad.                                                                                                                                                                                    (http://www.cancerresearchuk.org/prod_consump/groups/cr_common/@cah/@gen/documents/image/cr_015715.jpg) 

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Variation - Cloning

When cloning is used for reproduction, there is no variation in the offspring.

However, we can't yet clone humans. There are many ethicalissues surrounding whether we should even try. We can clone some organisms:

Plant cuttings: a small piece of a plant can grow into a genetically identical copy of the original       plant.

Tissue Culture: using small groups of cells from part of a plant to grow into a genetically identical                          copy of the original plant.

Embryo Transplants: splitting cells from a developing embryo before they specialise then                                              implanting into host mothers 

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Manipulating Genes

Your genome is the genetic code that make you unique. Genes are tiny. They are sections on chromosomesin every cell in your body so they are difficult to edit if you want to change anything. 

However, we are finding ways to do this...

Every organism on Earth uses the same genetic language for its genome, so a gene from 1 organism pasted into another organism will work.                                                                                                               

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Variation

Genetic Engineering: we use enzymes to cut genes from a chromosome which can then be pasted into chromosomesfrom other orgamisms.

Gene Therapy: we can modify the genes in adult cells in order to cure a genetic defect. This is done by using an empty virus to transport and insert the modified genes into the cells.

                                   

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