Biology Additional Science AQA

• Animal and plant cells
  • All Living things are made out of cells. 
  • Most cells have some structures in common these are: 
    • Nucleus- control the cells activities
    • Cytoplasm- where many chemical reactions take place
    • a cell membrane- controls the movement of materials in and out of the cell
    • mitochondria- energy is released during aerobic respiration
    • ribosome's- where protein synthesis takes place.
  • Plant and algal cells also have:
    • A rigid cell wall made of cellulose for support
    • chloroplasts that contain chlorophyll for photosynthesis; the chloroplasts absorb light energy to make food
    • a permanent vacuole containing cell sap
  • Algae has simple aquatic organisms similar to plant cells.

• Bacteria are very small and can only be seen with a powerful microscope
• Bacterial cells have a cell membrane and a cell wall which surround cytoplasm
• Bacteria do not have a nucleus so the genetic material is in the cytoplasm
• When bacteria multiply they form a colony. They can be seen with a naked eye. 
• Yeast is a single- celled organism
• Yeast cells have a nucleus, cytoplasm and a membrane surrounded by a cell wall.  

• Fat cells
• Three main adaptations
  • small amount of cytoplasm large amounts of fat
  • Few mitochondria, cell needs little energy
  • They can expand up to 1000 times there own size
• Root hair cells
• Two main adaptations
  • root hair increase surface area
  • have a large permanent vacuole
• Sperm cells
• Four main adaptations
  • Long tail for movement
  • full of mitochondria for energy
  • The acrosome stores digestive energy for breaking outer layers of the egg
  • large nucleus

- Molecules in gases and liquids move around randomly because of the energy they have. 

- Diffusion is the spreading out of particles of a gas, or any substance in solution.

-The net movement into or out of cells depends on the concentration of the particles on each side of the cell membrane.

- Because the particles move randomly, there will be a net (overall) movement from an area of high concentration to an area of lower concentration.

- The difference in concentration between two areas is called the concentration gradient. 

- The larger the difference in concentration, the faster the rate of diffusion.

Examples 

- the diffusion of oxygen into the cells of your body from the bloodstream of your cells (and using up oxygen)

- the diffusion of carbon dioxide into actively photosynthesising plant cells. 

- the diffusion of simple sugars such as amino acides from the gut through cell membranes. 

Tissues 

During the development of multicellular organisms the cells differentiate. Different cells have different functions. A tissue is a group of cells with similar structure and function. Animal tissues include

- muscle tissue, which can contract to bring about movement

- glandular tissue, to produce substances such as enzymes or hormones

- epithelial tissue, which covers some parts of the body

Plant tissues include

-  epidermal tissue, which covers the plant

- mesophyll which can photosynthesise

- xylem and phloem which transport substances around the plant

Organs

Organs are made of tissues The stomach is an organ made of:

- muscular tissue to churn the stomach contents

- glandular tissue to produce digestive juices

- epithelial tissue to cover the inside and outside of the stomach.

The leaf steam and root are plant organs which contain epidermal tissue, mesophyll, xylem and phloem. 

- Groups of organs form organ  systems to perform a particular function.

- The digestive system has several organs, including the small intestine.

The food you eat must be changed from insoluble molecules to soluble molecules. Then the soluble molecules can be absorbed into the blood. The digestive system does this. 

The digestive system is a muscular tube which contains:

- glands, such as the pancreas and the salivary glands

- the stomach and small intestine (digestion occurs)

- liver, produces bile

- small intestine where the absorption of soluble food occurs

- large intestine- water is absorbed from undigested food- forming faeces. 

• Plants and algae carry out photosynthesis. 
•                                 light energy
• Carbon dioxide+water➜  glucose+water
• algae and plant leaves contain chlorplasts which contain chlorophyll.
• light energy is absorbed by chlorophyll in the chloroplasts
• Energy is used to convert carbon dioxide from from the air and water from the soil into glucose.
• Some of the glucose is used imediately. 
• Some is converted into insoluble startch and stored
• Iodine solution- dark blue- starch is present

• Leaf adaptations
  • broad- bigger surface area light to fall on
  • chlorophyll- light energy
  • air spaces- carbon dioxide- cells and oxgen leave by diffusion
  • veins- water to cells

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  • Light- plenty of light PHS will take place, little or none phs will stop. brighter the light faster the rate of PHS
  • Temperature- temperature rises, rate of PHS increases as the reaction speeds up. Controlled by enzymes, enzymes denature once the temperature reaches 40-50℃.  The rate of photosynthesis will fall.
  • Carbon Dioxide levels- plants need carbon dioxide for glucose. Increasing carbon dioxide increases PHS. In a science lab, carbon dioxide can be increased artificially. This increases the rate of PHS. 
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Plants and algae make glucose when they photosynthesise. 

• This glucose is vital for their survival. 
• Glucose is broken down using oxygen.
• converted into insoluble starch for storage
• used for respiration
• converted into fats and oils for storage
• produce cellulose which strengthens cell walls
• produce proteins 
• Carbon dioxide and water are the waste products
• Plants and algal cells need mineral ions e.g nitrate ions
• This produces protein
• Plants absorb nitrate ions from soil
• Algae absorb nitrate ions from water

• Plant growers try to give their plants the best possible conditions by controlling their environment.
•  Evaluate the benefits in increasing growth and the increased cost of heating and lighting or carbon dioxide. 
• Greenhouses and polytunnels can be constructed to grow plants in an inclosed space.
• Heaters and lamp- photosynthesis will also increase
• May stop if temperature or light intesity too high
• Adding C02 air- rate of photosynthesis will also increase 
• Nitrate ions- added to soil- proteins
• Expensive- biomass indoors and outdoors without extra factors

• Factors affecting living organisims:
  • Temperature- limiting factor PHS and growth in plants. 
  • Nutrients- level of mineral ions big impact on distribution of plants. Venus flytraps thrive nitrate levels are low. Most other plants struggle. 
  • Amount of light- limits PHS. 

• amount of water- important for all organisms- rains in dessert, plants will grow- food for animals. 
• amount of carbon dioxide- affect plant growth and avalible food 
• amount of oxygen- water animals affected- some live at low oxygen levels.

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  • Quantative data
  • random quantative sampling- quadrat
  • sampling along a transect
  • Quadrat- square frame- wood or metal- subdivided into a grid. Several are placed randomly- count nymber of plant and animal. 
  • Sample size is important- large field, enough random quadrats must be place- sample size covers enough of the field. 

• estimate- mean per square metre Transect is not random. Line marked between two points, quadrat placed every five metres, organisms counted. Physical factors- could be measured. Habitat + organisms in it.

• investigations- difficult
• done over long period of time, not all variables can be controlled
• control variable- valid investigations
• repeatable- repeats and same results
• reproducible- check results 
• Reproducible- repeated by another person- same results
• sample size- important factor
• too small- not represantative
• larger- we can trust

• Protein molecules- long chains- amino acids
• folded produce specific shapes- shape of protein depends on function
• Proteins can be
  • structural components muscle or tissue
  • hormones
  • antibodies
  • catalysts
• Chemical reactions controlled by catalysts
• enzymes- biological catalysts speed up reactions
• large proteins and the shape vital for function
• shape other molecules fit- active site
• substrate- held in active site conncected to molecule/broken down
• Enzymes can
  • build large molecules from many smaller ones e.g building starch from glucose molecules
  • change one molecule into another one e.g. convert one type of sugar into another
  • break down large molecules into smaller ones e.g. all the digestive enzymes do this. 

Enzyme reactions are similar to other reactions when the temperature is increased. 

• Reactions take place faster when it is warmer. At higher temperatures the molecules move around more quickly and so collide with each other more often, and with more energy. 
• If the temperature gets too hot the enzyme stops working because the active site changes shape. We say that the enzyme becomes denatured. 
• Each enzyme works best at a particular pH value. Some work best in acid conditions, such as the stomach, such as the stomach, but othersneed neutral or akaline conditions. 
• If the pH is too acidic or alkaline for the enzyme, then the active site could change shape. Then the enzyme becomes denatured. 

• Your digestive system produces many enzymes.
• Have to be kept at 37 degrees.
• They also have to be kept at the right pH. 
• E.g Protease-in stomach-acid conditions in pancreas- alkaline conditions
• Secrete protease enzymes to digest protein- work best in an acid ph. 
• stomach produces hydrochloric acid from the same glands- 3l per day. 
• allows protease enzymes to work effectively- kills most bacteria. 
• thick layer of mucus-coats stomach walls and protects them from being digested
• A few hours later- small intestine
• some enzymes made in pancreas or small intestine.
• Liver- makes a greenish-alkaline liquid called bile. 
• stored in gall blader
• As food goes into small intestine-squirted with bile-neutralises acid from stomach-semidigested food alkaline=ideal conditions
• enzymes must have a large surface area-not a problem with carbs-fats stay as gloubules-difficult for lipase to digest-bile emulsifies-fatty acids and glycerol. 

• In the home- biological detergents-remove stains-contain proteases and lipases.
• Break down the proteins and fats. 
• Work at lower temperature to stop the enzymes denaturing.
• In industry- baby foods-predigest-protease enzymes-easier to get amino acids.
• Carbohydrases-starch into sugar
• Starch is made by plants e.g corn-very cheap-enzymes-cheap source of sweetnes
• Making fuel from plants-isomerase-change glucose into fructose
• fructose is sweeter than glucose-used in slimming food. 
• Advantages and disadvantantages
• industry-high temperatures and pressures- expensive equipment-lots of energy
• Enzymes-catalyse reactions low temperatures-cheap to run
• denatured at high temperature- 45 degrees- pH needs to be kept controlled
• Enzymes-expensive to produce-pure enzymes substrate more easily-more expensive

• When biological detergent-factory staff developed allergies-reacting to enzyme dust.
• Enzymes were put in tiny capsules-allergies stopped
• 2008-allergies were not because of the detergent.
• Enzymes and medicine
• Diagnose disease-liver is damaged or diseased-liver enzymes may leak into blood stream-doctors can test your blood for the enzymes.
• Diagnose and control disease-diabetes have too much glucose-glucose in urine-colour change on test *****-chemical indicator-placed in urine sample-enzyme catalyses-breakdown of any glucose -***** changes colour any enzymes present
• Cure disease-pancreas-damaged/diseased-can't make enzymes-lipase-enzymes are in special capsules-stop them being digested.
• Heart attack-streptokinase-injected-dissolves clots in ateriesof your heart wall-reduces amount of damage to heart.
• enzyme-treat blood cancer children-cancer cells-one type of amino acid-take it from body fluids-speeds up breakdown of amino acid-cancer cells can't get there-die-normal cells can make amino acid-not affected

• One of the most important enzyme controlled processes. Occurs constantly in animal and plant cells. 
• Glucose reacts with oxygen to produce energy. This energy is vital for everything that goes on in the body.
• Glucose+oxygen➜carbon dioxide+water+(energy)
• Aerobic respiration involves a lot of chemical reactions. 
• These reactions take place in the mitochondria of your cells. 
• They are tiny rod shaped parts (organelles).They have a folded inner membrane, which provides a large surface area for reactions to occur. The number of mitochondria indicates how active a cell is. 
• Living cells need energy-basic functions of life. 
• They build large molecules smaller ones to make new cell materials. 
• Most of this is used to respire.
• The sugars, nitrates and other nutrients built into amino acids. 
• In animals, energy is used to make muscles contract.
• Muscular activities use energy. 
• Mammals and animals keep their bodies at a constant temperature. 
• Energy to keep warm, hot days energy to sweat and keep your body cool. 

• muscles use a lot of energy
• muscle tissue-made from protein fibres
• muscles store glucose as glycogen-can be converted to glucose rapidly during exercise
• glucose+oxygen-carbon dioxide+water(+energy)
• exercise-many muscles contract harder-produce increased amouns of Co2-needs to be removed
• several changes-heart rate increases-arteries dilate (widen)
• increase blood flow-increases oxygen production and rate that Co2 is removed
• breathing rate increases-more oxygen brought to your body-picked up by red blood cells-oxygen-exercising muscles-more co2 removed from blood.

• In extreme exercise your muscle cells can become short of oxygen. Breathing rate and heart rate increase but this is not always enough-anaerobic respiration takes place, respiration without oxygen. In anaerobic respiration, glucose is not broken down completely. It produces lactic acid instead of carbon dioxide and water.  Using your muscle fibers for a long time can cause muscle fatigue. This means they stop contracting efficiently. One cause of muscle fatigue is the build up of lactic acid, blood flowing through your muscles removes lactic acid.
• glucose➜lactic acid (+ energy)

The waste lactic acid you produce during anaerobic respiration is a problem. You cannot simply get rid of the lactic acid by breathing it out you have to break it down to produce carbon dioxide and water. This needs oxygen. 

The amount of oxygen you need to break down the lactic acid into  carbon dioxide and water is called oxygen debt.The bigger the debt, the longer you will stay out of breath. 

Cell Division and Growth

New cells are needed for growth, and to repair new cells and damaged tissue. The new cells must have the same genetic information, so they can do the same job. 

All cells have a nucleus, containing instructions to make new cells, tissues and organs. They instructions are carried in the form of genes. 

A gene controls a characteristic or part of a characteristic of your body. It is a section of DNA. Different forms of the same gene are known as alleles. The genes are grouped together on chromosomes. A chromosome may carry several hundreds or thousands of genes. 

You have 46 chromosomes in the nucleus of your body cells. They are arranged in 23 pairs. One of each pair is inherited from your father, and one from your mother. Your sex cells (gametes) have only one of each pair of chromosomes. 

Mitosis

The cell division in a normal body produces two identical cells this is called mitosis. As a result of this all your body cells have the same chromosomes. Which means they have the same genetic information. In asexual reproduction, the cells of the offspring are produced by mitosis. Mitosis works because before a cell divides it produces new copies if the chromosome in the nucleus. The cell then divides once to form two genetically identical cells. 

E.g. Your skin, about 300 million body cells die every minute. 

• Type of cell division that results in half the number of chromosomes. 
• Takes place in the reproductive organs of animals and plants. 
• Female gametes and male gametes are made in the reproductive organs made by meiosis. 

• Meiosis is a type of cell division which halves the chromosome number- this produces our gametes. 
• Gametes have only one copy of each chromosome. When fertilisation occurs the egg cell provides half the chromosomes and the sperm cell provides the other half= 46.

• There are two cell divisions, which is how you end up with four gametes containing half the original number of chromosomes. 
• Things are ‘mixed up’ creating more variation. All the gametes are unique and different from one another causing variation.

• Variety is added at fertilisation- new genetic material is added. 
• Crossing over of chromosomes at lining up phrase. 
• The combination of genes in the new pair (after fertilisation) will contain alleles from each parent, producing different characteristics. 

Unspecialised cells- they have the ability to divide and change  into many different types of cells where they are needed.

Human Stem cells and found in embryonic tissue and in some adult tissue and in some adult tissue including bone marrow. 

Stem cells divide and form the specialised cells that form your various tissues and organs. 

When an egg and a sperm cell fuse to form an embryo, they form a single new cell. The cell divides and soon the embryo is a hollow ball of cells. The inner cells are embryonic stem cells which will eventually give rise to every type cell in your body. 

• Many people suffer and die because various parts of their body stop working properly. Spinal injuries cause paralysis, spinal nerves can not repair themselves. Millions of people would benefit if we could replace damaged body parts.
• In 1998 there was a scientific breakthrough by two american scientists. They managed to culture human embryonic stem cells that were capable of forming other types of cells.
• Scientists hope that embryonic stem cells cam be encouraged to grow into almost any different type of cell needed in the body, ie) new nerve cells. 

Stem cells- What’s the problem?

• No-one is entirely sure how the embryonic cells are switched on and off, and how to form particular types of tissue. 
• Ethical issues- embryonic cells are from aborted embryo’s or from spare embryo’s in fertility treatment. 
• Violation of human rights- embryo is not able to give its permission. 
• There is a concern that embryonic stem cells may cause cancer if used to treat the sick, as it has been seen in mice. 
• Stem cell research is slow, expensive, difficult and hard to control. 

 Stem cells-The Future

• Other avenues have been found- using embryonic stem cells from umbilical cord blood. Avoids ethical issues.
• Therapeutic cloning- using somatic cells from a human to produce a cloned early embryo of themselves as a source of perfectly matched embryonic stem cells. 

Gregor Mendel

• Born in 1822 in Czechoslovakia.
• Was very poor so became a monk to get an education.
• Was fascinated by peas and breeding them.
• Many people believed that we were the way we were because we have a mixture of material from our parents.
• Mendel believed through his studies that sections of inheritance were passed down through the generations.
• His work was recognised 16 years after his death as outstanding- he found all this out without the use of microscopes, so he knew nothing of chromosomes or DNA.
• The work he produced is the backbone of all genetics.
• He was known as ‘The Father of Inheritance.’

How Mendel discovered Inheritance.

• By these crosses Mendel knew that certain traits were passed on were not just a mixture.
• He found that characteristics were inherited in clear and predictable patterns.
• Mendel explained his results by suggesting there were separate units of inherited material. He saw that some characteristics were dominant over others and that they never mixed together. 

Our unique genetic code.

• Our DNA is unique to us (unless you are an identical twin.)
• Our DNA code is similar to the members of our family. 
• These codes can identify us by a process called DNA fingerprinting.
• This process can produce a pattern which shows our DNA code.
• These patterns can be used to identify our DNA and are used for crime scenes and paternity testing. 

The long strands of DNA are made up of combinations of four different chemical bases. These are grouped into threes and each group of three codes for an amino acid. Each gene is made up of hundreds or thousands of these bases. The order of the bases controls the order in which the amino acids and are put together so that they make a particular protein for use in the body cells. 

A change or mutation in a single group of bases can be enough to change or disrupt the whole protein structure and the way it works. 

Definitions

Homozygous-an individual with two identical alleles for a characteristic, E.g. DD (homozygous dominant), dd.

Heterozygous- an individual with different alleles for a characteristic E.g. Dd, dd(heterozygous recessive).

Genotype- this describes the genetic make up of an individual regarding a particular characteristic e.g Dd,dd.

Phenotype- this describes the physical appearance of an individual regarding a particular characteristic, e.g. dimples, no dimples. 

• Not all diseases are infectious, sometimes they are caused by a problem in our DNA.
• These can be passed down from parents to child.
• They are known as genetic diseases or disorders.

Polydactyly

• Sometimes babies are born with extra fingers or toes
• The most common form of polydactyly is caused by a dominant allele. (P)
• It can be inherited from one parent who has the condition.
• If one of your parents has polydactyly and is heterozygous, you have a 50% chance of inheriting the disorder. 

Cystic Fibrosis

• Disorder which affects the lungs and pancreas. Over 8500 people in the UK have this disease.
• The body produces thick, sticky, white mucus which clogs the airways and lungs.
• This results in many bacterial lung infections.
• The reproductive system is also affected, so many sufferers are infertile.
• Digestive enzymes in the pancreas are not made properly, so food cannot be properly digested.
• The allele which causes the disease is recessive (f), and is carried by around 1 in every 25 people in the UK.
• People with only one copy of the gene will not be sufferer’s, only carrier’s they will not show any symptoms.
• For a child to have the disease, both parents must be either carriers or sufferers. 

• Embryonic stem cells offer the best chances of finding treatments for lots of different and serious illness. e.g Diabetes, Alzehimer's.
• Embryo's used are spares from fertility treatment-wasted anyway.
• Created from adult cells-never become babies
• Could use embryo's from umblicial cord- no destroyed embroys.
• Could be used to grow new tissues and organs for transplants. 
• Very experimental- could go wrong-cause further problems. e.g cancer
• All embryos have the potential to become babies
• Embryos cannot give permission
• Taking too long to create- time better spent on other treatments. 
• Ethics of screening
• Huntington's disease-causes death in middle age-genetic test-some people take it- help decide weather to marry and have family-others dont want to know
• Inherited disorder-developing embryos tested-affected- keep or abortion-prevents birth of child with serious problems. 
• Screened before implanted-embryos produced by IVF-single cell from each embryo-healthy embryos are implanted. 

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  • Fossils are the remains of organisms from many years ago that are found in rocks.
  • Fossils may be formed in different ways.
  • Fossils give us information about organisms that lived millions of years ago. 
  • It is very difficult for scientists to know exactly how life on earth began because there is little evidence that is valid. 
  • 1. The reptile dies and falls to the ground.
  • 2. The flesh rots, leaving the skeleton to be covered in sand or soil and clay before it is damaged. 
  • 3. Protected, over millions of years, the skeleton becomes mineralised and turns to rock. The rocks shift in the earth with the fossils trapped inside. 
  • 4. Eventually the fossil emerges as the rocks move and erosion takes place. 

• The fossil record is incomplete but we can learn alot from the fossils that exist.Some have changed a lot, some not at all, and others have become extinct.
• Extinction means that a species that once existed has died out. e.g. dinosaurs.
• Extinction can be caused by a lot of factors, but always involves a change in circumstances.
• A new disease may kill all members
• The environment changes
• New diseases are introduced
• A new predator may evolve which kills all the species
• A new competitor may evolve- original species left with too little to eat
• A single catastrophic event may occur which destroys the habitat e.g. a volcanic erruption.
• Natural changes in species over time

• Biggest influences are changes in survival
• Organisms that do well in one climate won't do well in the other extreme. e.g in a hot climate to in a cold ice age. They will become extinct through lack of food and being unable to reproduce.
• Species that cope well in cold climates will evolve and thrive by natural selection. 
• Changes to climate/environment been the main cause of extinction throughout history. 
• Fossil evidence shows there have been mass extinctions on a global scale. During which many species die out. 
• This evidence suggests that a single catastrophic event is often the cause of these mass extinctions. e.g Volcanic erruption or asteriods colliding with the earth.
• Most recent mass extinction-dinosaurs-65 million years ago-giant asteriod collided with earth in Mexico.
• Crater (180km diameter)-layer of rock formed from crater debries in countries around the world. 
• Further you move from crater-thinner the layer of crater debris
• Scientists found mineral only created when an asteroid hits.
• Asteriod impact caused massive fires, earthquakes, landslides, tsunamis-material blasted into atmosphere. Dust in atmosphere made everything dark. Plants struggled to survive and drop in temperature caused global winter. 

• Group of UK scientists published different ideas and evidence. They suggest that the extinction of the dinosaurs started sooner(137 million years ago)-much slower. 

• After a mass extinction, scientists have noticed huge numbers of new species appear in the fossil record. -Evolution
• If one population becomes isolated from another the conditions are likely to be different.
• The two populations might change so much overtime that they cannot interbreed sucessfully, a new species evolves.
• Most common way is by geographical isolation. Physically isolated by a geographical feature. e.g new mountain range, new river or an area of land becoming an island. 
• e.g When austalia seperated from the other continents-marsuipual carry their babies in their pouches. 
• Marsupials evolved-organisms varied Kangaroos and koala's evolved. 
• Competition resulted in evolution of other mammals with more effiecient reproductive systems. 
• When a species evolves in isolation and is found in only one place in the world it is said to be endemic. E.g Borneo-400 new species, more than 25 mammals found only on the island. 
• natural genetic variety-contain a wide range of alleles controlling its characteristics-sexual reproduction and mutation. Alleles for population becomes isolated with new environmental conditions. alleles for charactersitics that enable organisms to survive and breed succesfully. 

• As a result of the different alleles the characteristic features of the isolated organisms will change.
• Eventually they can no longer interbreed with the original organisms and a new species forms. Specification
• Borneo, Australia, Galopagos Islands. If conditions in these isolated places are changed or habitat is lost,species that have evolved to survive could become extinct.
• Geographical isolation may involve very large areas or small regions. The animals and plants trapped within the crater have evolved in different ways to thos outside. 
• Very few people have been inside the crater, discovered 40 new species.