B1 -Understanding Organisms

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  • Created by: lucyannew
  • Created on: 13-04-16 20:45

Fitness and Health

Systolic = maximum pressure.

Diastolic = pressure between beats.

Increased by: alcohol. Decreased by: balanced diet. High blood pressure can cause a stroke. Low blood pressure can cause fainting.

Fitness = ability to do physical activity.

Health = being free from disease.

Fitness measures: strength, flexibility, stamina, agility, speed.

Carbon monoxide combines with haemoglobin in the blood reducing the oxygen-carrying capacity of the blood.

High saturated fat intake = build up of cholesterol = heart disease.

Plaque build up in the coronary arteries reduces blood flow to the heart muscle, making thrombosis more likely to happen.

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Health and Diet

Carbohydrates are made up of simple sugars, eg. glucose. They are stored in the liver as glycogen or converted into fats.

Proteins are made up of amino acids.

Fats are made up of fatty acids and glycerol. Fats are stored under the skin and around organs as adipose tissue.

PROTEIN EAR = 0.6 x body mass in kg

Too little protein leads to kwashiorkor. Meat and fish proteins are first-class proteins which contain all the essential amino acids that the body cannot make. Plant proteins are second-class proteins because they do not.

BMI = mass in kg/(height in m)squared

A healthy BMI is between 20 and 25.

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Protozoa -Malaria (Plasmodium=parasite, human=host, mosquito=vector), bacteriavirusfungus.


Pathogens produce symptoms by damaging cells or producing toxins. White blood cells contain antibodies which lock onto antigens on the surface of the pathogens, killing them.

In a blind trial the patient doesn't know if they are taking the real pill or a placebo. A double-blind trial means neither the patient nor the doctor knows.

Over time, bacteria can form resistance to anti-biotics, as a result of excessive use.

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The Eye (Diagram)


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Distant objects = ciliary muscles contract, suspensory ligaments tighten, lens becomes less rounded.

Red and green colour blindness is caused by a lack of specialised cells in the retina.

Long and short sightedness is caused by the lens or eyeball being the wrong shape. 

Short sight = eyeball too short, lens too thin. Image focused behind the retina.

Corrected by a concave lens.

Long sight = eyeball too longlens too thick. Image focused in front of the retina.

Corrected by a convex lens.

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Nerve Cells


Reflex action = stimulus > receptor > sensory neurone > central nervous system > motor neurone > effector > response

Spinal reflex = receptor > sensory neurone > relay neurone > motor neurone > effector

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Drugs, Smoking and Alcohol

Types: depressants (alcohol), painkillers (aspirin), stimulants (caffeine), performance enhancers (steroids),  hallucinogens (LSD).

Depressants bind the receptor molecules of the receiving neurone, blocking the transmission of nerve impulses across synapses.

Cilia are tiny hairs in the epithelial lining of the trachea. Cigarette smoke contains chemicals which stop the cilia from moving, meaning that mucus cannot be moved and dust and smoke particles collect in the trachea, irritating the epithelial lining. This causes a 'smoker's cough'.

Alcohol increases reaction times and damages the liver. When the liver breaks down toxic chemicals it becomes damage (cirrhosis of the liver).

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Negative feedback controls are used in homeostasis.

Vasoconstriction = when the body is too cold, blood vessels in the skin constrict to limit heat loss.

Vasodilation = when the body is too hot, blood vessels in the skin dilate, bringing more blood to the surface and increasing heat loss.

The optimum body temperature is 37 degrees.

Blood temperature is monitored by the hypothalamus gland in the brain. This works with a negative feedback system, allowing the body to respond accordingly and maintain homeostasis.

Blood sugar levels are controlled by insulin.

Type-1 Diabetes =pancreas doesn't produce any insulin. Treated by insulin injections.

Type-2 Diabetes =pancreas doesn't produce enough insulin, or body does not react to it. Controlled by diet.

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Controlling Plant Growth

Phototropism = a plant's growth response to light

Geotropism = a plant's growth response to gravity

Shoots are positively phototropic and negatively geotropic. Roots are negatively phototropic and positively geotropic.

Auxins = group of plant hormones which are made in the root and shoot tip.

More auxin is found in the shady part of the shoots; it elongates the cells causing the shoot tocurve towards the light.

Plant hormones can be used as:

selective weedkillers

rooting powder (to increase root growth of cuttings)

to delay or accelerate fruit ripening

to control dormancy in seeds

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Variation and Inheritence

Alleles = different versions of the same gene. They can be dominant or recessiveDominant alleles are expressed when present, but recessive alleles are only expressed in the absense of a dominat allele.

Humans have 23 pairs of chromosomes.

Sex chromosomes = chromosomes which determine the sex in mammals. Females have the sex chromosomes **, and males have the sex chromosomes XY. A sperm will carry either an X or a Y chromosome, which decides the sex of a fertilised egg. This is random.

Genetic variation is caused by mutations (random changes in DNA sequences). 

Genotype = genetic make-up.

Phenotype = which alleles are expressed.

Homozygous = when a person has identical alleles.

Heterozygous = when a person has different alleles.

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