Zusammenfassung der Ressource
Biology (B2)
- B2.1 - Cells, tissues and organs
- Animal and plant cells
- Human cells
Anmerkungen:
- Use this acronym to remember what is in a human cell:
Nice Chicken Curry Mild Rice
- Nucleus
Anmerkungen:
- Controls the cell's activities
- Cytoplasm
Anmerkungen:
- Many chemical reactions take place.
- Cell
membrane
Anmerkungen:
- Controls the movement of materials in and out of cell.
- Mitochondria
Anmerkungen:
- Energy is released during aerobic respiration
- Ribosomes
Anmerkungen:
- Protein synthesis takes place
- Plant cells
Anmerkungen:
- Contain all the things in a human cell, with these extra:
- Cell wall
Anmerkungen:
- Made of cellulose for support
- Chloroplasts
Anmerkungen:
- Contain chlorophyll for photosynthesis. The light energy is absorbed to make food.
- Permanent vacuole
Anmerkungen:
- Bacteria and yeast
Anmerkungen:
- -Very small and can only be seen by a microscope.
- Bacteria
Anmerkungen:
- Contains a cell membrane and cytoplasm surrounded by a cell wall.
- NO NUCLEUS - genetic material is in the cytoplasm
- Multiplied bacteria = bacterial colony
- Yeast
Anmerkungen:
- -SINGLE-CELLED organism
-Have a nucleus, cytoplasm and a membrane surrounded by a cell wall.
- Specialized cells
Anmerkungen:
- -Cells are specialized to carry out a specific function.
-The structure of the cell gives clues as to what it does.
- Muscle cells
Anmerkungen:
- Many mitochondria to create a lot of energy.
- Gland cells
Anmerkungen:
- Many ribosomes to create a lot of protein.
- Neurons
Anmerkungen:
- Specialized to carry impulses from receptors to the CNS.
- Diffusion
Anmerkungen:
- The spreading out of the particles of a gas, or of any substance in a solution.
- Concentration
Anmerkungen:
- NET MOVEMENT into or out of cells depends on concentration on either side of cell membrane.
- Difference in concentration between two areas is: CONCENTRATION GRADIENT
- Increasing diffusion
Anmerkungen:
- Rate is increased when:
-Distance is decreased.
-Surface area is increased.
-Concentration gradient is increased.
- Examples
Anmerkungen:
- Diffusion of oxygen into cells of body from the bloodstream.
Due to respiration of cells.
- Diffusion of carbon dioxide into actively photosynthesizing plant cells.
- Diffusion of simple sugars and amino acids from gut through cell membranes.
- Tissues and organs
- Tissues
Anmerkungen:
- A tissue is a group of cells with similar structure and function.
- Animal tissues
Anmerkungen:
- Muscle tissue - Can contract to bring about movement.
- Glandular tissue - To produce substances such as enzymes or hormones.
- Epithelial tissue - Covers some parts of the body.
- Plant tissues
Anmerkungen:
- Epidermal tissue - Covers the plant
- Mesophyll - Can photosynthesize
- Xylem and phloem - transport substances around the plant.
- Organs
Anmerkungen:
- Organs are made of several tissue types.
- The stomach
Anmerkungen:
- The stomach is an organ made up of:
-Muscular tissue to churn the stomach contents.
-Glandular tissue to produce DIGESTIVE JUICES.
-Epithelial tissue to cover the outside and the inside of the stomach.
- Organ systems
Anmerkungen:
- Groups of organs work together in an organ system.
- The digestive
system
Anmerkungen:
- The digestive system in humans is adapted to exchange substances with the environment.
- It includes:
-Glands, such as the pancreas and 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.
-The large intestine where water is absorbed from undigested food, producing faeces.
- B2.2 - Organisms in the environment
- Photosynthesis
Anmerkungen:
- During photosynthesis, light energy is transferred to chemical energy.
- Some of the glucose is converted into insoluble starch for storage.
- Equation
Anmerkungen:
- Carbon Dioxide + Water → Glucose + Oxygen
- 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
- Process
Anmerkungen:
- 1. CO₂ taken in by leaves, water taken in by roots.
2. Chlorophyll traps light energy.
3. Energy is used to convert the CO₂ and H₂0 to C₆H₁₂O₆
- Testing
Anmerkungen:
- -Testing leaves with iodine solution, to test for starch.
-Green patches will turn solution blue-black to show starch has been made.
- Variegated leaves
Anmerkungen:
- Different patches = difference in chlorophyll.
Green = Chlorophyll
White = No Chlorophyll
- Limiting factors
Anmerkungen:
- 3 limiting factors:
-Lack of light
-Cold (enzymes slower)
-Little carbon dioxide
- Experiments
Anmerkungen:
- Independent variable: Concentration of Carbon Dioxide
- Dependent Variable:
Volume of Oxygen produced.
- Control variables:
Light, temperature, type of plant
- How plants use glucose
Anmerkungen:
- -Converted into insoluble starch for storage.
-Respiration
-Converted into lipids and oils for storage.
-Produce cellulose which strengthens cell walls.
-Produce proteins.
- Ions
Anmerkungen:
- Plant and algal cells need a supply of mineral ions such as:
-Nitrate ions to produce protein.
--Plants absorb nitrate ions from soil.
--Algae absorb nitrate ions from the water in which they live.
- Making the most out
of photosynthesis
Anmerkungen:
- Plant growers can artificially control the environment to improve plant growth.
- To improve plant growth, the factors that need to be controlled are:
-Light intensity
-Temperature
-Carbon dioxide levels
- Organisms in their environment
Anmerkungen:
- The distribution of organisms is affected by environmental factors.
- -Temperature
-Availability of nutrients
-Amount of light
-Availability of water
-Availability of oxygen
-Availability of carbon dioxide
- Measuring the
distribution of organisms
Anmerkungen:
- Quantitative data is used to describe how physical factors might be affecting the distribution of organisms in a habitat.
- There are two ways to obtain quantitative data:
-Random quantitative sampling using a quadrat.
-Sampling along a transect.
- Quadrat
Anmerkungen:
- -A square from which may be subdivided into a grid.
-Several quadrats are placed randomly and the thing being investigated is counted in each one.
-It can be used to estimate the number of species or plant in a field.
- Transect
Anmerkungen:
- -This is not random. A line is marked between two points, and a random quadrat placed every 5 metres along the line.
-Supplies a lot of information about:
--Habitat
--Organisms in it.
- Sample size
Anmerkungen:
- In a large field, enough random quadrats are needed so that the sample is representative of the entire field.
- B2.3 - Enzymes
- Proteins, catalysts and
enzymes
- Proteins
Anmerkungen:
- -Made up of long chains of amino acids.
-Long chains are folded to produce specific shapes, which have a specific function.
- They can be:
-Structural components of tissues
-Hormones
-Antibodies
-Catalysts
- Enzymes
Anmerkungen:
- -Biological catalysts
-Large proteins and the shape is vital for its function.
-The 'active site' is the area where other molecules can fit.
- In a reaction, the substrate can:
-Be held in the active site.
-Be connected to another molecule.
-Be broken down.
- Enzymes can:
-Build large molecules from smaller ones.
--Starch from glucose molecules
-Change one molecule into another
-Break down large molecules into small ones.
- Factors affecting
enzyme action
Anmerkungen:
- -Reactions take place quicker if it is warmer.
--At higher temperatures the molecules move around more quickly and so collide with each other more often, with more energy.
(Learn this word for word)
- -Each enzyme works best at a particular pH value.
- Denaturing
Anmerkungen:
- If the temperature gets too hot, the active site CHANGE SHAPE, causing the enzyme to stop working.
- If the pH is too acidic or too alkaline for the enzyme, the active site could change shape.
- Digestion
Anmerkungen:
- -These enzymes are produced in the glands and in the lining of the gut.
-Enzymes pass out of the cells and come into contact with food.
-Digestion involves the breakdown of large, insoluble molecules into smaller soluble ones.
- Special enzymes
- Amylase
Anmerkungen:
- Produced in the salivary glands, the pancreas and the small intestine.
- Catalyses the digestion of starch into sugar in mouth and small intestine.
- Work best when the conditions are slightly alkaline.
- Protease
Anmerkungen:
- Produced by the stomach, pancreas and small intestine.
- Catalyses the breakdown of proteins into amino acids in the stomach and small intestine.
- Work best when the conditions are acidic.
- Lipase
Anmerkungen:
- Produced by the pancreas and small intestine.
- Catalyses the breakdown of lipids to fatty acids and glycerol.
- Work best when the conditions are slightly alkaline.
- Bile
Anmerkungen:
- -The liver produces bile.
-Stored in the gall bladder before being released into the small intestine.
-Bile neutralises the acid that was added to food in the stomach.
-This provides alkaline conditions in which enzymes in the small intestine work most effectively.
- Uses
- Biological detergents
Anmerkungen:
- -Contain proteases and lipases that digest food stains.
-Work at lower temperatures than ordinary washing powders.
-Saves energy and money spent on electricity.
- Baby foods
Anmerkungen:
- Proteases are used to pre-digest proteins in some baby foods.
- Fructose syrup
Anmerkungen:
- -Isomerase is used to convert glucose syrup into fructose syrup.
-Fructose is MUCH SWEETER so less is needed in foods.
-Foods are less fattening.
- Foods
Anmerkungen:
- Carbohydrases are used to convert starch into sugar syrup for use in foods.
- Industry
Anmerkungen:
- -Used to bring about reactions at normal temperatures and pressures.
-Traditional chemical processes require:
--Expensive equipment.
--A lot of energy (to produce high temperatures and pressures)
- High-tech enzymes
- Advantages
Anmerkungen:
- -Enzymes in biological washing powders are very effective at removing stains.
-Biological washing powders can be used at lower temperatures.
-Used in medicine to diagnose, control or cure disease.
-Industry, costs of equipment and energy can be reduced.
- Disadvantages
Anmerkungen:
- -Misuse of washing powders can cause allergic reactions on skin.
-Enzymes may enter waterways via the sewage system.
-Industrial enzymes are costly.
-Enzymes denature at high temperatures needed to kill pathogens in the washing.
-Fabrics such a wool are digested by proteases.
- B2.4 - Energy from respiration
- Aerobic respiration
Anmerkungen:
- -Takes place continually.
-Chemical reactions take place in the mitochondria and are controlled by enzymes.
- Equation
Anmerkungen:
- Glucose + oxygen → Carbon dioxide + water [+ energy]
- Uses
Anmerkungen:
- Energy released used to:
-Build larger molecules.
-Enable muscle contraction.
-Maintain a constant body temperature in colder surroundings.
-Build sugars, nitrates and other nutrients into amino acids and then proteins in plants.
- Experiment
Anmerkungen:
- -Measure volume of carbon dioxide produced.
- Effect of exercise
on the body
Anmerkungen:
- -During exercise muscles need more energy.
-More glucose and oxygen need to be transported to the muscles.
- Heart rate
Anmerkungen:
- Increase and the blood vessels dilate to allow more blood containing oxygen and glucose to reach the muscles.
- Breathing
Anmerkungen:
- Increase in breathing rate and depth of each breath to allow a greater uptake of oxygen and release of carbon dioxide in the lungs.
- Glycogen
Anmerkungen:
- Muscles store glucose at glycogen which can be converted back to glucose during exercise.
- Anaerobic respiration
Anmerkungen:
- When muscles work hard for a long time, they may have too little oxygen and become fatigued.
- Muscles use anaerobic respiration if they are short of oxygen.
- Anaerobic respiration doesn't break down glucose fully, therefore less energy is released from the glucose.
- Equation
Anmerkungen:
- glucose → lactic acid (+ energy released)
- Oxygen debt
Anmerkungen:
- In anaerobic respiration, lactic acid replaces carbon dioxide and water as the waste product.
- When the exercise is complete, the lactic acid MUST be broken down.
- The extra oxygen you need to oxidize the lactic acid into carbon dioxide and water is called oxygen debt.
- B2.5 - Simple inheritance in animals and plants
- Cell division
Anmerkungen:
- Necessary for the growth of an organism, or for the repair of damaged tissues.
- Mitosis
Anmerkungen:
- Two identical cells being produced from the original cell.
Mitosis = Making Identical Two
- Two identical cells being produced from the original cell.
46 chromosomes (2 sets)
Mitosis = Making Identical Two
- Chromosomes
Anmerkungen:
- Found in pairs and contain genes (alleles) which must be passed onto each new cell.
- Process
Anmerkungen:
- -Normal body cell has 46 chromosomes (23 pairs).
-Copies of these pairs are made.
-Then the cell divides once to form two genetically identical body cells.
- Meiosis
Anmerkungen:
- -Cells in reproductive organs divide by meiosis to form gametes.
-23 chromosomes (one set)
-Meiosis = Making Eggs
- Process
Anmerkungen:
- -Before division, a copy of each chromosome is made.
-The cell now divides twice to form four gametes.
-Each gamete has a single set of chromosomes with a different combination of genes.
- Sexual
reproduction
Anmerkungen:
- -Results in variation as the gametes from each parent fuse.
-Half genetic information from mother, half from father.
-In fertilization, a single body cell with new pairs of chromosomes form.
-Individual develops through mitosis.
- Differentiation
Anmerkungen:
- Most animal cells differentiate early in development and cell division is mainly for:
-Repair
-Replacement
- Plant cells can differentiate throughout the life of the plant as it continues to grow.
- Asexual
Anmerkungen:
- Asexual reproduction cells are produced by mitosis from the parent cell. They contain the SAME alleles as the parents.
- Stem cells
Anmerkungen:
- -Unspecialised.
-Found in human embryo and bone marrow.
-Differentiate into different types of body cell.
-Adult bone marrow stem cells - can differentiate into blood cells.-Hoped that stem cells could be used to cure diseases.
- Embryos
Anmerkungen:
- Embryonic stem cells can be used in medical research and treatments.
- Found:
-Spare embryos from IVF.
-Created from adult cells.
-Taken from the umbilical cord of newborn babies.
- Issues
- Economical
Anmerkungen:
- Very expensive to carry out research using embryonic cells.
- Ethical
Anmerkungen:
- -The research is experimental.
-Embryos have potential to become a baby and are destroyed.
-Embryo cannot give permission.
- Embryo screening
Anmerkungen:
- Involves tests to diagnose disorders before the baby is born.
- Results
Anmerkungen:
- -Sometimes parents decide to terminate the pregnancy.
-Others decide it isn't ethical and keep the baby.
- In IVF, only healthy embryos are implanted into the mother. Embryos carring FAULTY genes are destroyed, which isn't ethical.
- Mendel to DNA
Anmerkungen:
- A monk who worked out how characteristics were inherited.
- Genes
Anmerkungen:
- -Found on chromosomes.
-Control our characteristics.
-Short section of DNA.
- Genetic code
Anmerkungen:
- Each genes codes for a particular combination of amino acids which make a specific protein.
- DNA
Anmerkungen:
- -A very long molecule with a double helix structure (chromosomes).
-Every individual (bar identical twins) has different DNA.
- DNA Fingerprint
Anmerkungen:
- Unique DNA pattern which can be used to identify people.
- Inheritance
- Sex chromosomes
- Male
Anmerkungen:
- An X and a Y chromosome (XY)
- Female
Anmerkungen:
- Alleles
Anmerkungen:
- Genes controlling the same characteristic.
- Dominent
Anmerkungen:
- 'Masks' the effect of another allele.
- Recessive
Anmerkungen:
- The dominant allele 'masks' this allele, so it has no effect.
- Genetic diagrams
Anmerkungen:
- Biological models which can be constructed to predict and explain the inheritance of particular characteristics.
- Terminology
- Phenotype
Anmerkungen:
- Physical appearance of the characteristic (dimples or no dimples)
- Genotype
Anmerkungen:
- The genetic make-up, which alleles does the individual inherit.
(DD, Dd, dd)
- Homozygous
Anmerkungen:
- Both alleles are the same DD (homozygous dominant) or dd (homozygous recessive).
- Heterozygous
Anmerkungen:
- The two alleles are different, Dd.
- Genetic disorders
Anmerkungen:
- If an allele is recessive, the person must inherit two recessive alleles to have the disorder.
- If the allele is dominant, the person has to inherit only one dominant allele to have the disorder.
- Polydactyly
Anmerkungen:
- -Caused by a dominant allele.
-Where a baby is born with extra fingers or toes.
- Cystic fibrosis
Anmerkungen:
- -Caused by a recessive allele.
-Affects cell membranes and causes the production of thick sticky mucus.
- Carriers
Anmerkungen:
- People who carry a recessive allele.
- Punnet squares
Anmerkungen:
- Used to predict the chances of inheriting a disorder.
- B2.6 - Old and new species
- The origins of life on Earth
Anmerkungen:
- -Believed that the Earth is 4500 million years old and that life began about 3500 million years ago.
-There is DEBATE as to whether first live developed due to conditions on Earth, or whether simple life forms arrived from another planet.
- Fossils
Anmerkungen:
- -Fossils are remains of organisms from many years ago which are found in rocks.
-We can learn from fossils how different organisms have changed as life developed on Earth.
- -The fossil record is INCOMPLETE.
- How they are formed
Anmerkungen:
- -From hard parts of animals that do not decay easily (teeth, claws)
-From parts of organisms that have not decayed because some of the conditions for decay are absent (ice preservation).
-When parts of the organism are replaced by other materials, such as minerals, as they decay.
-As preserved traces of organisms (footprints, burrows).
- Destruction
Anmerkungen:
- Traces which were left are likely to have been destroyed by geological activity such as earthquakes.
- Soft-bodied
Anmerkungen:
- Soft-bodied organisms didn't leave fossils.
- Exploring fossil evidence
Anmerkungen:
- -The fossil record is incomplete.
-We can learn a lot from fossils which exist.
-Some organisms have changed a lot over time.
-Other have changed very little.
-Some have become extinct.
- Extinction
Anmerkungen:
- A species which once existed has completely died out.
- Factors
Anmerkungen:
- -A new disease may kill all members of a species.
-Change in environment.
-New diseases may be introduced.
-A new predator may evolve or be introduced to an area that kills and eats all of a species.
-A new competitor - original species may be left with little or nothing to eat.
-A single catastrophic event may occur which destroys the habitat.
-Natural changes in species occur over time.
- More about extinction
Anmerkungen:
- The biggest influences on a species survival are changes in the environment.
- Climate change
Anmerkungen:
- -A species which is very well adapted to a hot climate may become extinct in an Ice Age.
-There could be insufficient food or it is too cold to breed.
- -Climate change may:
--Make it too cold or hot.
--Make it too wet or dry.
--Reduce a species food supply.
- Fossil evidence
Anmerkungen:
- -Shows that there have been mass extinctions on a global scale.
-Many of the species died out over a period of several million years - a short time.
- -The habitat the species live in may be destroyed by catastrophic events such as a major volcanic eruption.
-The environment can change dramatically following a collision between a giant asteroid and Earth.
- The dinosaurs
Anmerkungen:
- No one knows why they have become extinct. Some ideas are:
-The collision of a giant asteroid caused huge fires, earthquakes, landslides and tsunamis. The dust which rose blocked out the sun, lowering temperatures and causing darkness. Plants could not grow.
-The extinction was a slower process due to sea ice melting and cooling the sea temperature by 9 degrees, therefore there was less plankton - less food available.
- Isolation and the evolution of new species
Anmerkungen:
- New species can arise form existing species if a group becomes isolated from the rest.
- Geographical isolation
Anmerkungen:
- -Could occur if an island separates from the mainland or if a new river separates two areas.
-Mountain ranges and old craters can isolate organisms.
- Speciation
Anmerkungen:
- Logical process:
Isolation → Genetic variation → alleles selected → interbreeding no longer possible → new species (speciation).
- Isolation
Anmerkungen:
- New species can occur following separation of two populations, as in geographical isolation.
- Genetic variation
Anmerkungen:
- Each population has a wide range of alleles that control their characteristics.
- Natural selection
Anmerkungen:
- -Occurs in both populations.
-The alleles that control the characteristics which help the organism to survive are selected.
-The organisms with these alleles will survive and breed.
- Evolution
Anmerkungen:
- If the environment, competitors, food supply and predators are different for each population, they will evolve differently.
- Interbreeding
Anmerkungen:
- SPECIATION has occurred when the two populations can no longer successfully interbreed.