Biology Unit 1

Carbohydrates - release energy

Fats - keep you warm and release energy 

Protein - for growth, cell repair and cell replacement 

Fibre - to keep everything moving smoothly through the digestive system

Vitamins and minerals - keep skin, bones, blood and everything else generally healhty 

Metabolic rate - rate at which chemical reactions in your body take place 

- muscle needs more energy than fat so more muscular people tend to have a higher metabolic rate

- bigger people are also likely to have a higher metabolic rate

- men in general also tend to have a higher metabolic rate as they are slightly bigger and tend to have a larger proportion of muscle 

Eating too much: 

• obesity - 20% or more over maximum recommended body weight 
• usually caused by bad diet, overeating and lack of exercise (sometimes hormonal problems)
• health problems - arthiritis, type 2 diabetes, high blood pressure, heart disease and cancers
• too much saturated fat leads to high blood cholesterol levels (risk of heart disease)
• too much salt can cause high blood pressure and heart problems

Eating too little: 

• health problems - slow growth (children), fatigue, poor resistance to infections and irregular periods (women)
• deficiency diseases are caused by a lack of vitamins or minerals e.g - lack of vitamin C can cause scurvy (causes problems in skin, joints and gums)

Inherited factors: - underactive thyroid gland (slows metabolic rate) or high blood cholesterol levels

**YOU CAN BE FIT (PHYSICALLY) BUT NOT HEALTHY!

Slimming claims 

Look out for: 

• Is the report a scientific study, published in a reputable journal? 
• Was it written by a qualified person (not connected with the product sellers)?
• Was the sample of people asked/tested large enough to provide reliable results? 
• Have there been any other similar studies that gave similar results? 

Diet and slimming products only work if you...

• If you eat less fat or carbohydrate than you use 
• Do more excercise to use more energy 

(some claims may be true but misleading, low fat bars may be low in fat but eating them and not changing the rest of your diet doesn't neccessarily mean you will lose weight)

Bacteria - very small living cells and make you feel ill by damaging your cells and producing toxins 

Viruses - aren't cells (much smaller) and replicate themselves by invading your cells and using its 'machinery' to produce copies of itself.. the cell then bursts and releases the virus (cell damage makes you feel ill)

Bodies defency system: 

• skin, hair and mucus in respiratory tract (stops nasties getting in)
• platelets clot blood quickly (prevent microorganisms coming in through cuts)

White blood cells:

• consume them (engulfs and digests)
• produces antibodies (lock onto and kill invading cells)
• produces antitoxins (counteract toxins)

Vaccinations 

•  inject dead or inactive pathogens into the body 
• body produce antibodies to attack them as they carry antigens 
• if the same microorganism enters the body again the white blood cells can rapidly mass produce the antibodies to kill off the pathogen before it makes you really ill 
• some vaccinations wear off over time so boosters are required 

Pros 

• help control infectious diseases
• prevents big outbreaks (epidemics)
• protects those who can't be vaccinated 

Cons 

• they don't always work 
• bad reactions to the vaccine can sometimes occur 

Painkillers and cold remedies - relieve/reduce symptoms 

Antibiotics - kill the bacteria without killing body cells (cure the problem)

Antibiotic resistance - bacteria can mutate and become resistant to the antibiotic, if imfection is treated the resistant strain will survive and reproduce. This strain could cause a serious infection that cannot be treated by antibiotics (e.g - MRSA that causes serious wound infections). To slow down the rate of these resistant strains developing, doctors should avoid prescribing antibiotics where possible. 

Investigating antibiotics 

• microorganisms are grown on a culture medium (agar jelly that contains carbohydrates, minerals, vitamins and proteins)
• hot jelly is poured into petri dish, inoculating loops are used to transfer microorganisms to the jelly, paper disks are soaked in antibiotics and placed on the jelly, antibiotic resistant bacteria will continue to grow arounf the disks. 
• loops need passing through a flame and the petri dish must have a lid taped on 

Semmelweis - believed doctors were spreading disease on their unwashed hands so made them wash their hands in an antiseptic solution before entering his maternity ward. This dropped the death rate of women during childbirth by 10% but because bacteria and them causing disease wasn't yet discovered he didn't have enough proof for people to believe him so once he left the hospital people stopped following his regime. 

New and scary dangers 

Bacteria 

• a new strain could occur that is antibiotic resistant and nobody would be immune to it so it could end up causing an epidemic 

Viruses 

• viruses mutate often so vaccines against them are hard to develop 
• worst case scenario is a new virus could develop and create a pandemic killing billions 

(pandemic = when a disease spreads all over the world)

• sense organs detect stimuli (a change in your environment you may react to)
• 5 different sense organs - eyes, ears, nose, tongue and skin 
• receptors - light receptors, sound receptors, smell receptors, taste receptors and skin is sensitive to pressure, pain and temperature change 
• a stimulus can be light, sound, touch, pressure, pain, chemical or a change in position or temperature 

Central nervous system 

• where all information from the sense organs is sent 
• where reflexes and actions are coordinated
• consists of only the brain and the spinal cord 
• neurones transmit information to the central nervous system 
• the central nervous system sends 'instructions' to the effectors (muscles and glands)

Synapse - the connection between two neurones where the nerve signal is transferred by chemicals which diffuse across the gap (the chemicals then set off a new electrical signal in the nect neurone)

Reflexes- automatic responses to certain stimuli which reduce the chances of being injured 

The Reflex Arc

• stimulus 
• receptor 
• sensory neurone 
• synapse 
• relay neurone 
• synapse 
• motor neurone 
• effector 
• response 

Hormones - chemical messengers that travel in the blood to activate target cells 

Hormones and Nerves 

Nerves 

• fast action (response)
• act for a short time 
• act on a precise area 

Hormones 

• slower action (response)
• act for a long time 
• act in a more general way 

Stage 1:  Day 1 - bleeding starts 

Stage 2:  Day 4 - 14 -  the uterus lining builds up 

Stage 3: Day 14 - an egg is released from the ovary 

Stage 4: Day 14 - 28 - the wall is maintained and if the egg isnt fertilised by day 28 then the cycle happens again 

FSH - produced by the pituiutary gland, causes an egg to mature and stimulates the ovaries to prodyce oestrogen 

Oestrogen - produced in the ovaries, inhibits the further release of FSH and promotes the release of LH

LH - produced by the pituitary gland and stimulates the release of an egg 

The pill (decreasing fertility)  - contains oestrogen (to stop the release of an egg) and progesterone (to stimulate the production of thick cervical mucus)

Pros - over 99% effective and reduces the risk of getting some types of cancer 

Cons - not 100% effective, can cause side effects and doesn't protect against STD's 

Increasing fertility - FSH and LH can be injected into a woman to cause an egg to mature and be released if their body can't do this propely for some reason 

Pros - helps women to get pregnant

Cons - doesn't always work, can be expensive and sometimes can result in multiples pregnancies 

IVF-collecting women's eggs and fertilising in a lab with a man's sperm before being implanted in to the womb once the embryos are tiny balls of cells (FSH and LH are given beforE)

Pros - can give an infertile couple children 

Cons - can cause reactions (hormones), multiple births can occur and could increase cancer risk

Auxin - a plant growth hormone that controls the growth near tips of shoots and roots 

• Shoots grow towards light (auxin accumulates more in shade and that side then grows faster)
• Shoots grow away from gravity (auxin accumulates on lower side which then grows faster)
• Roots grow towards gravity (auxin accumulates on lower side which in roots inhibits growth)
• Roots grow towards moisture (auxin accumulates on the side with more moisture which inhits growth that side) 

- response to light = phototropism

-response to gravity = gravitropism 

Plant hormone uses in agriculture 

• selective weed killers - made of plant growth hormones that affect broad leafed plants (weeds) but don't affect narrow leafed ones (grasses and cereals)
• plant cuttings don't alwasy grow in soil so adding rooting powder (that contains auxin) causes them to produce roots rapidly 

Bodily levels that need controlling - ion content, water content, sugar content and temperature 

Ion content - regulated by kidneys, if too many ions are taken in from food then the excess ions need to be removed. Some ions are lost in sweat and the kidneys remove any excess from the blood and get rid of them in your urine. 

Water loss - water is lost from the body through the skin as sweat, via the lungs in your breath and via the kidneys as urine. 

Body temperature - controlled by the brain, enzymes in the body work best at 37 degrees so your body tries to maintain this temperature. A part of your brain acts as a thermostat which is sensitive to blood temperature and recieves messages about skin temperature. 

Blood sugar level - a hormone called insulin helps maintain the right level of glucose in your blood so your cells get a constant supply of energy. 

DRUGS CHANGE YOUR BODY CHEMISTRY

Medicinal drugs - medically useful e.g - antibitoics, morphine, paracetamol (aren't all prescbribed)

Recreational drugs - used for fun (illegal and legal)

Performance enhancing drugs - improve a peron's performance in sport 

Anabolic steroids - increase muscle size 

Stimulants - increase heart rate 

Against drugs in sport - it's unfair and athletes may not be informed of the health risks they bring 

For drugs in sport - athletes have the right to choose if they want to or not and drug free sport isn't really fair anyway 

• tested on human cells and tissues in the lab or on whole animals for something that involves whole body systems 
• test it on live animals to determine if it works, it's toxicity and to find out the best dosage 
• test it on human volunteers in clinical trials (firstly healthy and then those with the actual illness after if all goes well)
• the optimum dose should then be found by this point 
• volunteers are put in two groups (unknown which groups) so some are given the actual drug and some are given a placebo allowing the doctor to see the actual difference made as this counts for the placebo effect 
• the trials are blind so the patient doesn't know if they are taking the real thing or not and even sometimes double blind so the doctor doesn't know either until after the results have been gathered 

Past errors - thalidomide was intended as a sleeping pill and was tested for that use but was later discovered effective for treating morning sickness in pregnant women. However, it wasn't tested for morning sickness so nobody knew it could pass through the placenta and cause limb abnormalities in the fetus. This therefore affected 10,000 babies of which around only half actually survived so the drug was banned. Now it is used to treat leprosy and other diseases. 

• illegal or legal 
• usually used for stress relief, enjoyment or relaxation 

Some studies link cannabis and hard drug use: 

• It is a "stepping stone" - the effects create the desire to try harder drugs 
• It is a "gateway drug" - it brings people into contact with drug dealers 
• It is all down to genetics - some people are more likely to take drugs so will also try other drugs

Smoking - causes disease of blood vessels, heart and lungs. The smoke causes cancer. Nicotine is addictive which is why it is hard to stop smoking. 

Alcohol - affects the nervous system by slowing down the bodies reactions. It leads to impaired judgement, poor coordination and unconsciousness. Excessive drinking can cause liver disease and brain damage. Alcohol is addicitve. 

Desert animals - save water and keep cool:

• large surface area compared to volume (lose more body heat)
• efficient with water (produce small amounts of concentrated urine and make little sweat)
• good in hot conditions (thin layers of body fat and a thing coat (store fat in one place))
• camouflage (sandy colour to avoid predators and sneak up on prey)

Arctic animals - reduce heat loss:

• small surface area compared to volume (reduces heat loss)
• well insulated (thick layer of fur and blubber for insulation (also an energy store))
• camouflage (to avoid predators and sneak up on prey)

Desert plants - adapted to having little water: 

• small surface area compared to volume (reduces water loss (cacti have spines instead of leaves)
• water storage tissues (store water in thick stem)
• maximise water absorption (shallow but extensive roots or deep roots to get ground water)

Deterring predators 

• armour (shells, spikes, thorns)
• poisons (bees and ivy)
• warning colours (wasps)

Extremophiles - adapted to like in seriously extreme conditions like super hot volcanic vents, very salty lakes or high pressure on the sea bed 

Organisms compete for resources to survive:

Animals - space, food, water and mates

Plants - light, space, water and minerals (nutrients) 

Environmental changes 

Living factors - change in occurance of infectious diseases, change in number of predators, change in number of prey/availability of food source and a change in the number of competitors 

Non-living factors - a change in average temperature, a change in average rainfall and a change in the level of air or water pollution 

Living indicators 

• lichen - indicate air pollution as the more different species of it the cleaner the air (sensitive to sulfur dioxide)
• invertebrates (mayfly larvae) - indicate clean water as sensitive to oxygen concentration 
• invertebrates (rat-tailed maggots and sludgeworms) - indicate polluted water as they live in high level of pollution water 

Non-living indicators

• satellites - measure sea surface temperature and the amount of snow and ice coverage 
• weather stations - tell us the atmospheric temperature 
• rain gauges - measure rainfall
• dissolved oxygen meters - discover how water pollution is changing by measuring dissolved oxygen in water 

How the energy 'dissapears' - 

• energy is sourced from the sun 
• plants use some energy to respire and photosynthesise 
• animals use energy for respiration which supplies energy for everything (e.g movement)
• some energy is lost the surroundings as heat 
• energy is lost through an organisms waste materials 

Elements are cycled back to the start of the food chain through decay:

• broken down by microorganisms and are therefore put back into the soil 
• works best in warm and moist conditions and faster with lots of microorganisms with plenty of oxygen available which makes compost bins ideal as the recreate the ideal conditions 

Same species have differences - due to variation 

Genetic variation 

• characteristics are determined by genes inherited by your parents (some from the mother and some from the father)
• the combining of genes causes genetic variation (no two species are genetically identical except identical twins)
• some characteristics are determined only by genes (e.g eye colour, blood group, inherited disorders)

Environmental variation 

• the environment causes differences (e.g suntan, yellow leaves) 
• this variation comes from the conditions something lives in 

**most characteristics are a combination of both genetic and environmental factors 

• cell
• nucleus
• genetic material (chromosomes)
• genes
• long length of DNA/short length of chromosome 

**there can be different versions of the same gene which give different versions of the characterustic (e.g brown or blue eyes)

**the different versions are called alleles 

Sexual reproduction - the fusion of male and female gametes. Due to there being two parents, the offspring contain a mixture of both their parents genes. 

Asexual reproduction - there is only one parent. There is no fusion of gametes, no mixing of chromosomes and no genetic variation between parent and offspring. The offspring are genetically identical to their parents - they are clones. 

The chromosomes in asexual reproduction split in half to form two sets of 'half-chromosomes', the DNA then replicates itself to form two identical cells with complete sets of chromosomes. 

Plant cloning 

Cuttings - gardeners take cuttings from good parent plants and plant them to produce genetically identical copies. These plants can be produced quickly and cheaply.

Tissue culture - a few plant cells are put in a growth medium with hormones and they grow into new plants that are clones of the parent. These can be made quickly, in little space and can be grown all year.

Animal cloning 

Embryo transplants - sperm cells from the male and egg cells from the female are taken and the egg is artificially fertilised by the sperm. The embryo that develops is split many times to form clones before any cells become specialised. The cloned embryos can then be implanted into lots of other surrogate mothers to grow and be born. 

Adult Cell cloning  - take an unfertilised egg and remove its genetic material. A complete set of chromosomes from an adult body cell is the inserted into the empty egg cell. It is stimulated by an electric shock which causes it to divide like a normal embryo. It is the implanted into the surrogate mother to grow into a genetically identical copy.

Issues surrounding cloning: 

• creates a reduced gene pool meaning a new disease could wipe out a whole species 
• the animals may not be as healthy as normal ones 

• useful gene is cut from one organisms chromosome using enzymes 
• enzymes cut another organisms chromosome and insert the useful gene

Transferring genes into animals and plants

• GM crops have their genes modified to make them resistant to viruses, insectsor herbicides
• sheep have been modified to produce substances like drugs in their milk that can be used to treat human diseases 

Genetic engineering controversy 

• worries of long term effects 

GM crops controversy 

• may reduce biodiversity 
• not everyone believes they are safe 
• transplanted genes may get into other things and create resistances (e.g superweeds)

Natural selection - Charles Darwin:

• random mutation causes variation 
• they are better adapted so can get food 
• survive 
• reproduce 
• genes are passed on 

Mutations - a change in an organisms DNA. Sometimes they can be useful as provide a beneficial characteristic which is then passed on due to natural selection. The mutation the accumulates in the population over time. 

Not everyone agreed with Darwin because... 

• it went against religious beliefs 
• he couldn't give a good explanation as we didn't know anything about genes or mutations then 
• there wasn't enough evidence to convince many scientists 

Lamarcks theory

• believed if a characteristic was used a lot in the organisms lifetime it would become more developed 
• he believed these acquired characteristics would then be passed on to the nect generation