B2:Biology;Unit 2

  • Variation & Cloning
  • Organisms & Environment
  • Speciation
  • Cells & Cell Structure
  • Respiration
  • Proteins
  • Cell Division & Inheritance
  • Photosynthesis
  • Created by: simmie
  • Created on: 18-01-13 19:03

Variation & Cloning

Cutting:Is cheap and quick.
Cutting process:Take a piece from an old parent plant. Dip it in hormonal rooting powder and plant it in compost.

Tissue Culture:Take a few cells from a plant & place on a petri dish with algar.-Makes 1000' of copies.

Sexual Reproduction:Joining of male and female gametes.
Mixture of genetic information from parents leads to variation in offspring.
(genes from both parents-variety in offspring)

Inherited Factors:eye colour;hair colour;attached ear lobes;tongue rolling;migraines.
Acquired Factors:piercings;scars;tattoos;dyed hair;suntan;foreign language.

Asexual Reproduction:No fusion of gametes.One individual needed.
No mixing of genetic information-no genetic variation.
Genetically Identical Individuals-Clones.
*Bulbs in daffodils,runners in strawberries,tubers in potatoes


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Variation & Cloning (2)

Economic,Social & Ethical Values-Gm Crops (genetically modified crops):Increased yields,more profit,cheap produce.
Effect on populations of wild flower 7 insects.
Effects of eating GM Crops on human health.
Is it right to try and influence the evolution direction on plants?
Reduced gene pool.

Gene: Short sequence of DNA to code for one characteristic.
Gamete:A sex cell eg. sperm,pollen.
Clone:Genetically identical copy.

Bt(Bacillus thuringiensis):Bacterium that kills insects.
*The gene from the DNA from the bacteria cell that produces toxins is cut out using enzymes.The cut out gene from the bacteria cell is inserted into plant cells using enzymes.

Embryos for Transplants:*Splitting apart cells from a developing animal embryo before the y become specialised,then transplanting the identical embryos to their host mothers.
-Animals will all grow similiar size and produce similiar yields of milk/meat. However they a re more likely to be wiped out by a disease.

Adult Cell Cloning: -Nucleas removed from unfertilised egg cell.
-Nucleas from adult body cell (skin cell) is inserted into an egg cell.
-An electric shock causes the egg cell to divide to form embryo cells.
-Embryo cells contain same genetic information as adult skin cell.
-When embryo is developed into a ball of cells, it's inserted into adult female womb to continue development.

*Used to clone pets; Grow tissues or organs for patients

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Organisms & Environment

Sampling of weeds using a quadrant: Split field into equal sized fractions.Give each fraction a number.Use a random number generator to choose sample areas.
Transect technique compared to quadrant sampling: Quadrant tells you about one specific spot-useful for sampling daisies.
Transect allows you to see patterns as you move along a line from point A to point B.

Physical factors affecting organism numbers:
Temperature-Affects organisms metabolic rate.Some organisms cant tolerate extreme temperatures.
Nutrients-Essential for the growth of plants and microorganisms.Low concentration of nutrients-Organisms struggle and die.
Light-Source of photosynthesis.Low intensities of light-Plants grow slowly.
Water-All organisms require water.Chemical reactions in/out of cells occur in water.Absence of water-cells & organisms die.
Oxygen-Aerobic respiration.Oxygen limit in soil/water-plant roots cant grow/absorb mineral ions.Aquatic organisms struggle to respire.
Carbon Dioxide-Essential for photosynthesis.Limited in environment where there are many plants-reduce growth in plants.

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Organisms & Environment (2)

Quantitative Data:
Sampling:Study distribution of species;Size of are being studied;No. organisms living there;Where those organisms live.
Although, it's very time consuming to count individual organisms;They may move;There may be too many;Sample chosen should be representative of the whole area;It should provide valid data;Sample should be used to estimate total population;Estimated population should be the same size.
Square frames used to mark out specific areas.
Grid=10cm x 10 cm
Used:Which species present;No. of species;Percentage cover of species.
Random Sampling:
Regular grid using tape.

Generate random numbers using computer etc.
Determine co-ordinates.
No bias by investigator.
Ensures results are valid.
Investigate population of species in the quadrant.
Repeat many times.

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Organisms & Environment (3)

Transects-Use When:
Changes in distribution of population of an organism.
Two neighbouring habitats eg. grassland to woodland.
Factor lead to zonation.

  • Choose the start and end position of the transect.
  • Determune direction & length of transect.
  • Lay down tape to mark out transect.
  • Sample the organisms along the line.
  • Perform parallel transects to ensure results are reliable.
  • Take recordings of the factors that influence distribution.

Mean:add all results then divide by the amount of results.
Median:the middle value of a list.
Mode:the most common value in a list.

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Evolution & Speciation

Evolution leads  to the development of lots of different species. (change in species if the environment changes)
Speciation is the development of a new species.-occurs when populations of the same species become different, so that they cannot produce fertile offspring.

Why species become extinct?:Environment change;New predator;New disease;Compete for food;Catastrophic event (volcanic eruptions);New species development;New competitors.
If an organism cannot evolve quickly enough to become better adapted to the change they become extinct.
If they do evolve, it is likey to develop into a new species.
Origin of life:The first ever organisms were simple celled, similar to bacteria. These life forms rarely survived as fossils.-So scientists cannot be certain of how life began,they can only develop theories.
Fossils:-Only fossils can tell us that extinct animals existed.Fossils show us how organisms change after time.
Fossils form if hard parts such as teeth do not decay; If a condition for decay is absent;If parts are replaced by other materials during decay;Burrows,rootlet traces & footprints.

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Evolution & Speciation (2)

Species is defined as a group of organisms that are capable of producing fertile offspring.
New species arise as a result of:
Isolation-Two populations of species become seperated.

Genetic Variation:Each population has a wide range of alleles that control characteristics.

Natural selection:In each population alleles that control the characteristics help the organisms to survive are selected.-Individuals with the most beneficial alleles are most likely to survive.More likely to reproduce and pass on genes. Beneficial alleles become more common in future generations.

  • Individual organisms within a particular species show a wide range of variation because of differences in their genes.
  • Individuals with the most suited characteristics are the most likely to survive & breed successfully.
  • Genes that have enabled organisms to survive are then passed on to the next generation.

Speciation:The populations become so different that succesful interbreeding is no longer possible. They have now become seperate species.

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Evolution & Species (3)

Darwins Theory:Natural selection states that all species of living things formed from simple life forms that first developed more than 3 billion years ago.

Why Darwin's theory was gradually accepted?: The theory challenged wether or not God created the animals and plants that live on Earth.
There was insufficient evidence at the time.
The mechanism of Inheritance was not discovered until 50 years after the theory was published.

Darwin's & Lamark's Theories:
Similarities: include the fact that the inherited/acquired feature was passed onto the next generation.
Differences: include the fact that Darwin mentioned that features were controlled by inheritance;However Lamark suggested thtat the features wer acquired during their lifetime.
Darwin said that differences were brought about due to mutations;However Lamark said that differences were brought about due to change in the environment.

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Cells & Cell Structure

All living things are made up of cells.
Cells are the smallest unit of life.
Animal Cells:
Nucleas-Controls the activity of the cell.
Membrane-Controls what goes in/out of the cell.
Mitochondria-Respiration takes place to release energy.
Rhibosomes-Site of protein synthesis.
Cytoplasm-Where chemical reactions take place.
Plant Cells:
Membrane:Controls what goes in/out of the cell.
Nucleas-Controls activities of the cell.
Mitochondria-Respiration takes place.
Cytoplasm-Chemical Reactions occur.
Cell Wall-Strengthen the cell,withstands water pressure.
Chloroplasts-Site of photosynthesis.
Vacuole-Cell sap is held.
Bacteria Cell:Cytoplasm;Membrane;Cell Wall;No nucleas.
Yeast Cell:Nucleas;Cytoplasm;Membran;Cell Wall.

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Cells & Cell Structure (2)

Cells may be specialised to carry out a particular function.

Red Blood Cell:Large surface area/membrane to carry more oxygen.
Root Hair Cell:Large surface are to absorb water/minerals.
White Blood Cell:Changes shape to engulf microbes.
Sperm Cell:Tail to swim.
Egg Cell:Carries female DNa,Nourishes embryo in early stages.
Nerve Cell:Long nerve fibre to carry messages to other cells.

Diffusion is the movement of particles in a gas/solution subsatnce from an are with high concentration to a low concentration.
(The greater the difference in concentration, the faster the rate of diffusion)
Solutes:Particles in a solution eg.glucose
Solvent:liquid in which the particles are dissolved eg.water.
Solute and solvent molecules move around randomly. Solutes move in and out of cells using diffusion.

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Cells & Cell Structures (Tissues,Organs) (3)

Multi cellular organisms: Develop systems for exchanging material.
Cells differentiate so that they can perform different functions.

Tissue: A tissue is a group of cells with similar structure or function.
Organs are made up of tissues.
One organ may contain several tissues.
Organ systems are groups of organs that perform specific functions.
Eg.-The Digestive System
Humans and other mammals exchange substances with the environment.
The digestive system includes:
Glands such as the pancreas, salivary glands which produce digestive juices.
Stomach and small intestine where digestion occurs.
Liver which produces bile.
Small intestine where the absorption of soluble food occurs.
Large intestine, where water is absorbed from the undigested food, producing faeces.

Plant Organs Include:The stem;The leaves;The roots.
Plant Tissues:Epidermal tissues , which cover the plant;Mesophyll,carries out photosynthesis;Xylem&Phloem,transports substances around the plant.

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Respiration occurs in small reactions. Each reaction is controlled by an enzyme.
Aerobic:Uses oxygen
Anaerobic:Uses no oxygen.

Key Life Process:Movement;Respiration;sensitivity;Growth;Reproduction;Excretion;Nutrition.

Changes in Body When Exercising:Heart Rate Increase;Rate and Depth of Breathing increases;Arteries supplying to muscles widen;Arteries going to the skin widen (dilate);Glycogen in muscles breaks down into glucose;Increase in sweating;Muscles contract.

Changes in Body When Exercising: Faster transport of glucose and oxygen to muscles; Faster removal of lactic acid and carbon dioxide from cells;Increased rate of diffusion of oxygen and carbon dioxide at lungs; Faster rate of respiration in cells,releasing energy faster; faster release of heat from the body preventing enzymes from denaturing.

Aerobic Respiration: Glucose reacts with oxygen , producing carbon dioxide and water as by products. Takes place continuously in plants and animals.
Glucose + Oxygen --- Carbon Dioxide + Water + Energy

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Respiration (2)

Respiration occurs in all living cells.
Respiration happens in the mitochondria structure.
The inner surface of the mitochondria is highly folded to increase the surface area for enzymes.

These structures are found within the cytoplasm of a cell.
Chemical Reactions take place in the cytoplasm.Enzymes control all chemical reactions.
It is important for cells to regulate their temperature, because the enzymes denature,respiration would stop happening and the cell dies.
There is no difference in respiration, it happens day and night in all cells.

Aerobic respiration may stop because oxygen may not get to the cells quick enough and energy is still needed. Muscles stop contracting as efficiently.

The energy in respiration is used to build larger molecules from smaller ones eg. glycogen from glucose.
Enables muscles to contract in animals.
Maintains a steady body temperature in mammals,birds.
Builds up sugars,nitrates and nutrients into amino acids which are then producing proteins in plants.

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Respiration (3)

-Stored glucose in the muscles.
During exercise the glycogen are broken down into glucose in the muscles.This can increase the amount of glucose that can be respired.

Anaerobic Respiration:
If insufficient oxygen is reaching the muscles, the muscles respire anaerobically to obtain energy.
Anaerobic respiration is the incomplete break down of glucose and produces lactic acid.
As the break down of glucose is incomplete, much less energy is being released as when respiring aerobically.
Glucose --- Lactic Acid + Small Amount of Energy 

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Respiration (4)

Lactic Acid:-Is poisonous. We can only tolerate small amounts of it in our body.
If muscles are subjected to it for long periods of time or for vigorous activity they become fatigued.
Blood flowing through the muscles removes lactic acid.
During/after exercise we breath heavily to oxidise the lactic acid.
Lactic acid + Oxygen --- Carbon Dioxide + Water

The extra oxygen produced when respiring anaerobically is called oxygen debt.
During anaerobic respiration the heart continues to pump faster.

-The breathing rate remains high.Which delivers the extra oxygen to the muscles.This pays back the oxygen debt.

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Cell Division & Inheritance

Characteristics are passed on from one generation to another in both animals and plants.

Genetic material:
In a a nucleas of the human body their are 23 pairs of chromosomes.
We inherit one pair of 23 chromosomes from each of our parents.

DNA:Double Helix is the shape of DNA that makes up a chromosome. A gene is a small section of DNA.
Each gene codes for a specific combination of amino acids to create proteins.these proteins determine our characteristics. Some characteristics are controlled by a single gene.
Two Roles of DNA:
Replicate prior to cell division.
Its code is used to synthesise proteins.
DNA fingerprint is a unique code to everyone apart from identical twins. A fingerprint will be different in everyone.

A gene is a short section of chromosome DNA that codes for one feature eg.eye colour.

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Cell Division & Inheritance (2)

Mitosis is the repair/growth of tissues (replacement tissues).
The nucleas divides into two to form two genetically identical cells .This results into two identical nuclei.}
Some cells undergo cell division again and again.
some cells carry out their function then they die.

  • New cell forms.
  • Cell grows.
  • Cell specialises and carries out its function.
  • DNA is copied.
  • Cell prepared to divide.
  • Mitosis and cell division.

New body cells produced:
-When the animal is growing
-To repair damaged tissues
-To replace worn out tissues

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Cell Division & Inheritance (3)

Asexual Reproduction: The cells of the offspring produced by asexual reproduction are produced by mitosos from the parental cells.
They contain the same genes as the parents.

Cell Diffrentiation: results when some genes are turned off and some genes are turned on.
Once cells are specialised they carry out their role.
Animal cells diffrentiate at different stages.
Plants retain the ability to diffrentiate throughout life.
In mature animals, cell division is mainly restricted to repair and replacement.

Stem cells are cells that have not yet be specialised by the process of diffrentiation.
Main Animal Sources:Embryonic (IVF);Umbilical Cord;Adult Stem Cells (Bone Marrow)
Embryonic is the best source as they can be any cell in the body.The others are limited.
Treatment with these cells may help cure conditions such as paralysis.
many people are concerned about the use of human embryos to treat disease.
Some people believe that embryos have the potential to become a baby, and they should be used in this way.

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Cell Division & Inheritance (4)

Meiosis- Ensures variation of offspring.

Gametes are sex cells (sperm & egg cells)
Sperm is formed in the testes.Egg cells are formed in the ovaries.

A cell with a full number of chromosomes in pairs divides to form cells with half the number cell of chromosomes.
During Meiosis:Copies of the chromosomes are made;The nucleus divides twice to form nuclei;The cell divides twice to produce four gametes (each has a single set of chromosomes).

  • Parent Cell.
  • DNA Replicates.
  • 2 Daughter Cells.
  • 4 Daughter Cells.

When gametes join at fertilisation, a single body cell with new pairs of chromosomes is formed.
A new individual then develops by this cell repeatedly dividing by mitosis.

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Cell Division & Inheritance (5)

Asexual reproduction leads to very little variation.
Organisms that reproduce asexually create new individuals by mitosis.
They are genetically identical to the parent.
They may develop differently due to changes in their environment.

Sexual reproduction leads to much more variation.
Meiosis ensures that all gametes have the same genes, but have a different selection of alleles.
It's random which sperm fertilises which egg.
Therefore all individuals (except identical twins) produced sexually are genetically different.

Dominant alleles only need to be inherited from one parent to be seen.
Recessive alleles must be inherited from both parents to be seen.

Genotype: Is the code used (combination for alleles) Aa.
Homozygous Genotype: Two identical alleles.
Heterozygous Genotype: Two different alleles for a gene.
Phenotype:Is what is displayed in the environment. Genetic & Environmental factors.

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Cell Division & Inheritance (6)

Mendel was a Monk.Founder of genetics.He studied the pea plant.
-He noticed that certain characteristics that were shown in two pea plants, were not always shown in their offspring. However the characteristics sometimes reappeared in the next generation.
-He proposed the idea that each individual inherits a set of factors each from their parents.

Mendel's ideas were not accepted in the past because:-
He wasn't a scientist.
Technology wasn't as advanced.
His theory defied religious beliefs about God.

When we are conceived we receive one copy of each gene from each parent.
Therefore we have two copies of every gene but there may be two different alleles.
Different combinations of alleles may lead to differences in the characteristic.

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Cell Division & Inheritance (7)

Sex Determination: In human body cells, one of the 23 pairs of chromosomes carries the gene which determines sex.
In females the sex chromosomes are the same (**)
In males the sex chromosomes are different (XY)

Embryo Screening is taking a cell from an embryo (IVF) and looking for a genetic disorder.

Cystic Fibrosis:
Each gene codes for a particular combination of amino acids which make a specific protein. If a different amino acid is sequenced a different protein is made which might cause more mucus to be released at the cell membrane.

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Proteins are made at ribosomes in all body cells.

Examples of Proteins:
Keratin in nails & hair.
Melanin in skin pigment.
Haemoglobin in red blood cells.

Bile is a protein which is a strong alkali. It is made in the liver. It is stored in the gall bladder. Bile breaks up (emulsifies) large fat into smaller fat droplets to increase the surface area for the enzyme lipase to work on.

Bile neutralises the stomach acid and makes chyme slightly alkali providing the optimum conditions for the small intestine enzymes work at.

Protein molecules are made up of long chains of amino acids. These long chains are folded to produce a specific shape that enabless other molecules to fit into the protein.

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Proteins (2)

Enzymes are biological catalysts.
Catalysts increase the rate of chemical reactions.
Enzymes are protein molecules made up of long chains of amino acids.

  • Enzyme available with an empty active site.
  • Substrate binds to the enzyme.
  • Substrate is converted to products.
  • Products are released (glucose,fructose)

Activation Energy: Energy required for a chemical reaction to take place. Enzymes reduce the activation energy.

Effect of temperature on enzymes:
The rate of enzyme controlled reactions increases as the temperature increases.
The enzyme and substrate move around and collide more often, therefore shaping the enzyme.The active site becomes a different shape and the substrate does not fit any more. It's then described as denatured.
Effect of PH on enzymes:
Affects the shape by affecting the forces that hold the enzyme molecule together. A change in PH denature the enzyme.

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Proteins (3)

Hormonesare proteins. Eg. Insulin
Hormones are released into the blood from the glands.
They have specific shapes, and attach to molecules on the cell membrane of specific target cells.

Antibodies are made of proteins.
They are released by white blood cells.
They have a specific shape that attaches to antigens.
antigens are chemicals that pathogens carry/release.

Enzymes in industry:
Enzymes enable industrial reactions to happen at low temperatures.
Supplying heat is expensive.When enzymes are used the process becomes cheaper.
Enzymes are sensitive  to temperature and PH changes.
Temperature and pH need to be carefully monitored and controlled, which can be expensive.

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Proteins (4)

 Catalyses starch into glucose. The enzyme is secreted from the salivary glands, pancreas and small intestine. The enzyme works best in a weak alkali pH 8.

 Catalyses proteins into amino acids. The enzyme is secreted from the stomach, pancreas an small intestine. The enzyme works best in a strong acid pH 2.

 Catalyses fats into fatty acids and glycerol. the enzyme is secreted from Small intestine and pancreas. The enzyme works best in a weak alkali pH 8.

Enzymes can be used in slimming products;baby foods;biological washing powders.

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Synthesis=Making of (glucose)
PHOTOSYNTHESIS=Making glucose using light.


  • Light energy is absorbed by chlorophyll.
  • Which is found in chloroplasts.
  • Energy is used by converting carbon dioxide and water into glucose.
  • Oxygen is released as a by product.
  • Carbon Dioxide + Water --------(light energy)---------Glucose + Oxygen

Photosynthesis happens in the leaves mainly. It mainly occurs in the mesophyll, which contain a lot of chloroplasts.

Glucose produced in photosynthesis may be converted into insoluble starch for storage.
Plant cells use the glucose for respiration;produce fat/oil storage;produce cellulose;produce proteins.

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Photosythesis (2)

Factors that limit the rat of photosynthesis:

  • Temperature- a low temperature will limit the rate as the molecules will move less and therefore the reaction happens slower.
  • Carbon Dioxide- a shortage of CO2 will limit the rate as fewer molecules will be available for the reaction.
  • Light Intensity-A shortage of light means there is less energy to power the reaction.

Farming Practices: Farmers can artificially manipulate the environment in which they grow plants.

  • Growing plants in greenhouses/ polythene tunnels.
  • controlling the temperatures in greenhouses using heaters + ventilation.
  • Artificially increase carbon dioxide levels.
  • Control the light using fluorescent lamps.

By doing this plants grow faster, and certain plants can be grown out of season Eg. tomatoes.

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Chelsey Mitchell


Amazing! Perfect revision notes

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