Edexcel I Gcse Biology Flashcards
What characteristics do all living organisms share?
NutritionRespirationExcretionResponse to surroundingsMovementHomeostasisReproductionGrowth and development
Common features shared by plants
Has a nucleusMulticellularAutotrophic (self-feeding; carry out photosynthesis)Cell wall made of cellulose
Common features shared by fungi
Has a nucleusMulticellularCell wall made of chitinHeterotrophic (feed on other organisms)Body is usually organised into a mycelium made from hyphaeFeed by extracellular secretion of digestive enzymes onto food material and absorption of the organic products(examples: mushroom, mold, puffball)
Common features shared by animals
Has a nucleusMulticellularHeterotrophic (feed of other organisms)Cells don't have a cell wallHave nervous coordination
Common features shared by bacteria
Have a cell wall (not made from cellulose)Cells have no nucleusSingle-celledMicroscopicNo nucleus (but contain DNA)Some carry out photosynthesis but most feed of other living or dead organisms(examples: lactobacillus bulgaricus, pneumococcus)
Common features shared by protoctists
MicroscopicSingle-celled(examples: amoeba, chlorella, plasmodium)
Common features shared by viruses
Small particles (smaller than bacteria)ParasiticCan reproduce only inside living cellsCan infect every type of living organismNo cellular structure (have a protein coat and contain either DNA or RNA)(examples: tobacco mosaic virus, influenza virus, HIV virus)
What is a pathogen?
a bacterium, virus, or other microorganisms that can cause disease
Examples of pathogens
FungiBacteriaProtoctistsViruses
Levels of organisation within organisms (order of ascending size)
OrganellesCellsTissuesOrgansSystems
What are the organelles present within a typical animal cell?
NucleusMitochondrionCell membraneCytoplasm
What is the cytoplasm and its function?
A jelly-like material that contains dissolved nutrients and salts and organelles. It is where many of the chemical reactions happen.
What does the nucleus do?
Contains genetic material, including DNA, which controls the cell's activities.
What does the cell membrane do?
It is permeable to some substances but not to others and so controls the movement of substances in and out of the cell.
What do mitochondria do?
Organelles that contains the enzymes for respiration, and where most energy is released in respiration.
What are the organelles visible in a typical animal cell?
CytoplasmNucleusVacuoleMitochondrionCell membraneCell wallChloroplast(organelles in bold are only present in plant cells)
What does the chloroplast do?
Contains green pigment, chlorophyll, which absorbs light energy for photosynthesis. Has enzymes needed for photosynthesis.
What does the cell wall do?
Provide structure and protection.Made of cellulose only in plants
What does the vacuole do?
Filled with cell sap to help keep the cell turgid (stiff and swollen)(N.B. Animall cells may have vacuoles, but these are small and temporary)
Which organelles are present in both animal cells and plant cells?
NucleusCell membraneCytoplasmMitochondrion
What elements are present in carbohydrates?
Carbon, hydrogen, oxygen
What elements are present in proteins?
Carbon, hydrogen, oxygen and nitrogen
What elements are present in lipids?
Carbon, hydrogen, oxygen
What is starch a polymer of?
Glucose
What is protein a polymer of?
Amino acids
What are lipids made of?
Fatty acids and glycerol
Describe the test for glucose
(Called Benedict's test)Heat test solution with Benedict's reagent to 90°C for 5 minutes.Positive result turns solution brick red colour
Describe test for starch
Iodine solution turns blue-black in presence of starch.
What are enzymes?
Biological catalysts in metabolic reactions
What conditions can affect the functioning of enzymes?
TemperaturepH(Enzymes get denatured in high temperatures/pH; function best at optimal temperature and pH)
Diffusion definition
Diffusion is the net movement of molecules or atoms from a region of high concentration to a region of low concentration.
Osmosis definition
Osmosis is the movement of water from an area of high water potential to an area of low water potential across a partially permeable membrane.(water potential = water concentration)
Active transport definition
The movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy
What is turgidity and why do plant cells need to be turgid?
Turgidity is when a cell is 'swollen' with water. This acts as a means of support
What factors affect the rate of movement of substances into and out of cells?
Surface area : volume ratioTemperatureConcentration gradient
Photosynthesis word equation
Carbon dioxide + water â glucose + oxygen (using light energy and chlorophyll)
Photosynthesis balanced equation
6COâ + 6HâO â CâHââOâ + 6Oâ
What is photosynthesis?
The process by which carbon dioxide and water are converted into glucose by green plants, using energy from the sun and chlorophyll.
Describe the energy changes that take place within photosyhnthesis
Light energy â chemical energy
What factors affect the rate of photosynthesis?
COâ concentration (rate of diffusion; therefore rate of usage for photosynthesis)Light intensity (amount of light energy available)Colour of light (will not work in green light because is reflected of green leaves)Temperature (optimal temperature for enzymes)
Structure of leaf (top to bottom)
Waxy cuticleUpper epidermisPalisade mesophyllSpongy mesophyllLower epidermis(Guard cells & stomata)Waxy cuticle
What does the waxy cuticle do?
Protects leaf from microorganisms and water
How is the waxy cuticle adapted?
Thin and made of wax - protects leaf without blocking out light
What does the palisade layer do?
Contains many chloroplasts to carry out photosynthesis
How is the palisade layer adapted?
Close to top of leaf (absorbs more light)Contains many chloroplasts (more photosynthesis)
What does the spongy layer in leaves do?
Gaseous exchange
How is the spongy layer in leaves adapted to its function?
Air spaces allow carbon dioxide to diffuse through leafAir spaces increase surface area
How are leaves adapted?
Large surface area (absorb more light)Thin (short distance for carbon dioxide to diffuse into leaf cells)Chlorophyll (absorbs sunlight to transfer energy into chemicals)Network of veins (support leaf; transport water and carbohydrates)Stomata (allow carbon dioxide to diffuse into leaf)Xylems and phloems near the palisade cells (water is readily available and glucose can be transported away efficiently)
How to plants uptake mineral ions?
Through roots by active transport.
What do plants need nitrate ions for?
Making amino acids (and proteins)
What do plants need magnesium ions for?
Making chlorophyll
What mineral ion do plants need to make chlorophyll?
Magnesium ions
What do plants need phosphate ions for?
Making DNA
What mineral ions do plants need to make DNA?
Phosphate ions
What do plants need potassium ions for?
Respiration and growth
What are all the sections of a balanced diet?
CarbohydrateProteinLipidVitaminsMineralsWaterDietary Fibre
What is a balanced diet?
A combination of foods that provides the correct proportions of all the various food molecules for any particular individual at any particular stage of their life.
Why do we need carbohydrates?
Glucose is needed for respiration (and hence energy)
What foods do we get carbohydrates from?
Bread, pasta, potatoes
Why do we need protein?
Building new cells/Growth
What foods do we get protein from?
Meat, fish, eggs(some beans and nuts)
Why do we need lipids?
Long term energy storage (in adipose tissue)Electrical insulation of nerve cells
What foods do we get lipids from?
Red meat, processed foods, vegetable oils
Examples of minerals we need
CalciumIron(others not needed for GCSE)
Why do we need calcium as a mineral?
Making healthy teeth and bones
Why do we need iron as a mineral?
Making haemoglobin
What foods do we get iron from?
Red meat
Examples of vitamins
Vitamin AVitamin CVitamin D(other not needed for GCSE)
What is vitamin A called?
Retinol
What is retinol?
Vitamin A
Where do we get vitamin A from?
Carrots, red peppers, swede
What is vitamin A needed for?
Vision (it is used to make the pigment in retina cells)Healthy growthImmune system
Vitamin A deficiency
Night blindness (generally poor vision, especially at night)
Where do we get vitamin C from?
Citrus fruits (oranges, lemons etc.)
What is vitamin C needed for?
Producing collagen
Vitamin C deficiency
Scurvy
Where do we get vitamin D?
UV light from the sun
What is vitamin D needed for?
Absorption of mineral ions in small intestines
Vitamin D deficiency
Rickets
What is dietary fibre?
Cellulose that can't be digested by mammals (cellulose is passed through gut into large intestine)
Why do we need fibre?
Prevents constipation
What foods do we get fibre from?
Wholegrain bread, vegetables
Why do we need water?
Replace water loss by sweating and urineSolvent for all metabolic reactions
What factors affect daily human energy requirements?
Activity level (more active people need more energy)Age (older people need less energy)Pregnancy (pregnant people need more energy)
Structures of human alimentary canal (start to finish)
MouthOesophagusStomachSmall intestineLarge intestinePancreas (separate from start-finish order)
How does the mouth aid in digestion?
Mechanical digestion (chewing)Salivary glands secrete saliva, which contains amylase (begins digestion of starch in mouth)
How does the oesophagus aid in digestion?
Carries food from throat into stomachUses peristalsis
Ingestion
Taking food into the body through the mouth.
Digestion
The chemical and mechanical breakdown of food. It converts large insoluble molecules into small soluble molecules, which can be absorbed into the blood.
Peristalsis
Waves of muscle contraction that pass along the gut. Behind the food, circular muscles contract, longitudinal muscles relax, and the gut narrows pushing the food along.
Absorption
The movement of a substance across a cell membrane by means of diffusion or osmosis.
Assimilation
When soluble food molecules are absorbed from the blood into cells, and are used to build new parts of cells.
Egestion
The removal of undigested food as faeces.
Amylase
Digests starch into maltose. Produced by the salivary glands and pancreas.
Maltase
Digests maltose to glucose. Produced by the wall of the small intestine.
Lipase
Digests lipids to glycerol and fatty acids. Produced by the pancreas.
Proteases
An example would be Pepsin, which digests proteins to peptides. Pepsin is produced in the stomach.
Mouth
Where food is broken down mechanically into smaller pieces that have a large surface area.
Saliva
Moistens food and contains the enzyme amylase which begins the breakdown of starch in the mouth.
Oesophagus
Tube connecting the mouth and the stomach.
Stomach
Holds food for several hours. It's wall secretes hydrochloric acid and digestive enzymes.
Sphincter
Ring of muscles which holds food in the stomach until it is ready to enter the small intestine.
Hydrochloric acid
Secreted by the stomach wall to kill bacteria which can enter the body via food we have eaten.
Small intestine
Divided into the duodenum and the ileum, it's function is to breakdown food and absorb nutrients into the bloodstream.
Duodenum
First section of the small intestine which is responsible for the breakdown of food using enzymes.
Ileum
Final section of the small intestine which is adapted to absorb the products of digestion into the bloodstream.
Villi
Tiny projections from the lining of the ileum. Villi increase the surface area of the ileum to aid absorption.
Microvilli
Tiny projections from the surface of each villus, that help to increase the surface area of the villus.
Describe 4 adaptations of the small intestine that allow it to absorb digested food efficiently
1. Villi and microvilli increase surface area 2. Long length increases surface area 3. Rich blood supply helps carry absorbed molecules away 4. Thin wall means short diffusion distance
Large intestine
Absorbs the remaining water from semi-digested food to leave a semi-solid waste material called faeces.
Rectum
Stores faeces which are expelled via the anus.
Pancreas
Responsible for making several digestive enzymes that work in the small intestine.
Bile
A green alkaline liquid produced by the liver. It has two functions 1. To emulsify lipids 2. To neutralise stomach acid
Gall bladder
Stores bile.
Define 'population'
A group of organisms of one species that interbreed and live in the same place at the same time.
Define 'community'
An ecological unit composed of a group of organisms or a population of different species occupying a particular area.
Define 'habitat'
The environment within which organisms live
Define 'ecosystem'
A community of organisms living in a particular habitat together and their interactions with each other and with the physical components of their environment.
How can you estimate the population size of an organism in two different areas?
Quadrats are used to give a random estimate of population sizes in two or more different areas.
What is a trophic level?
A trophic level is the position that an organism occupies in a food chain.
What name is given to a plant that makes its own energy?
Producer (autotroph)
What is a producer?
Producers are organisms that occupy the lowest trophic level and can convert sunlight (photoautotrophs) or use chemical reactions (chemoautotrophs) to create energy.
What is a consumer?
Consumers are organisms that can't produce their own energy, so have to feed on organisms from lower trophic levels for energy.
In a food web, who is the primary consumer (and subsequently the secondary and tertiary consumers etc.)?
The primary consumer feeds off the producers (the secondary consumer off the primary, the tertiary off the secondary etc.)
What are decomposers?
A decomposer is an organism whose ecological function involves the recycling of nutrients by performing the natural process of decomposition as it feeds on dead or decaying organisms.
What do food chains represent?
Food chains represent the feeding relationships between organisms in an ecosystem.
Why do we use food webs?
Normally food chains interlink with each other, so we group them together into food webs.
What is a pyramid of numbers?
A pyramid of numbers is a diagram that displays the relative population sizes of different trophic levels. (The number of organisms are sampled, not individually counted.)
Give an example of producer that would cause a pyramid of numbers to be inverted.
Trees or large producers can cause pyramids of numbers to be inverted.
What is a pyramid of biomass?
Pyramids of biomass represent the amount of dry mass at each trophic level. (These can be inverted if the reproductive rates of organisms in the ecosystems are very different.)
What is the main issue with using pyramids of biomass?
Pyramids of biomass only provide a snapshot view of the ecosystem.
How do we get around the issues of pyramids of biomass and numbers?
We can use pyramids of energy which are never inverted (this would contradict the first law of thermodynamics).
What do pyramids of energy represent?
Pyramids of energy represent the energy content of each trophic level.
What is energy consumption of trophic levels measured in?
kJ/m3/year (kilojoules per metre cubed per year)
How much energy is transferred from one trophic level to the next and why?
10% (approx.) of energy is transferred from one trophic level to the next.Energy is used up by organisms in respiration (movement, and maintaining body temperature for warm-blooded animals), and is lost in faeces through indigestible matter (mammals can't digest cellulose, so it passes through our systems).
What issues does water quality pose in fish farms?
Fish produce faeces and ammonia as waste products (you don't want to be eating that).Fish will also use up the oxygen in the water in enclosed tanks.
How is water quality maintained in fish farms?
Water quality is maintained by filtration of ammonia in enclosed tanks (ammonia naturally is swept away by the tide in tidal fish farming).Water is oxygenated in enclosed tanks (there will always be a supply of fresh water in tidal farming).
What issues does intraspecific competition in fish farms pose?
Big fish occasionally eat the smaller fish of the same species, especially aggressive (or psychotic) fish.Big fish will also outcompete smaller fish for oxygen in water and for the food.
How is intraspecific competition controlled in fish farms?
Each tank will only have fish of the same age, so they will grow at roughly the same rate and be roughly the same size and maturity.
What issues does interspecific competition pose in fish farms?
Larger species will outcompete smaller species for food and oxygen.Species with higher reproductive rates will also outcompete the slower reproducing species for food and oxygen.Some fish species may also end up predating other fish species.
How is interspecific competition in fish farms controlled?
Different species are placed in different tanksTanks are covered on top and a fine mesh is used on the sides so the fish can't be eaten by birds or other predators (seals, sharks etc.)
How is disease controlled in fish farms?
Antibiotics added to foodSpraying insecticide (that won't accumulate in food chain)
How are waste products removed in fish farms?
Filtration of NH3/ammonia (when enclosed; otherwise it'll diffuse away with tide)Removal of faeces
Describe the feeding in fish farms.
Lots of protein in food (to compensate for lack of muscle development due to lack of swimming)Antibiotics added to foodLess food fed more frequently (excess food --> eutrophication)
Why is selective breeding used in fish farms?
Muscular/high muscle massFast growth (yield increases)Placid fish
How do fish farms affect the environment?
Fish may escape and outcompete or interbreed with other species (reduces biodiversity)Parasties & pathogens spread quicklyExcess food and waste --> eutrophication
Stages in water cycle
CondensationCloudsPrecipitationTranspirationPercolationGroundwaterOceanRun-offEvaporation
Stages in carbon cycle
RespirationPhotosynthesisDecompositionCombustionFossilisationFeeding
Stages in nitrogen cycle
LightningHaber ProcessDeath/decomposition (via decomposers)Nitrogen fixing (via symbiotic and asymbiotic nitrogen fixing bacteria)Nitrification (via nitrifying bacteria)Denitrification (via denitrifying bacteria)Active transport (NO3- uptaken by plants via active transport)
What are the biological consequences of air pollution by sulfur dioxide and carbon dioxide
Acid rain (sulfuric/carbonic acid. Pine trees lose needles, attacks limestone, leaches Al3+ ions from soil, irritant to fish, kills all life in freshwater ecosystems)Greenhouse effect
LH (luteinising hormone)
Triggers release of egg from ovary
FSH (follicle stimulating hormone)
Secreted by pituitary glandCauses egg to mature in ovaryStimulates ovaries to release oestrogen
Oestrogen
Secreted by ovariesStops FSH production so that only one egg maturesStimulates pituitary gland to release LH
Progesterone
Maintains thickness of uterine wall
Aerobic respiration word equation
Glucose + oxygen â Carbon dioxide + water + energy
Anaerobic respiration (in animals) word equation
Glucose â Lactic acid + energy
Anaerobic respiration (in plants) word equation
Glucose â Ethanol + carbon dioxide + energy
Aerobic respiration balanced chemical equation
CâHââOâ + Oâ â 6COâ + 6HâO + energy
Anaerobic respiration (in animals) balanced chemical equation
CâHââOâ â 2CâHâOâ + energy
Anaerobic respiration (in plants) balanced chemical equation
CâHââOâ â 2CâHâ OH + 2COâ + energy
When does respiration happen?
All the time
When does photosynthesis happen?
In the daytime/in the presence of light
How are alveoli adapted for gas exchange by diffusion?
- Close to capillaries- Thin walls- Large surface area- Large quantity
What is the role of stomata in gas exchange?
They allow gases such as carbon dioxide, water vapour and oxygen to move rapidly into and out of the leaf
The blood's composition
- Red blood cells- White blood cells- Platelets- Plasma
What is the blood plasma's function?
Transports:â Waste products e.g. COâ, ureaâ Hormonesâ Heat energyâ Digested food
How are red blood cells adapted for their functions?
- Dip in structure allows oxygen to bind easier- Haemoglobin is adapted to specially bind to oxygen to form oxyhaemoglobin
What is a pathogen?
A biological agent that causes disease or illness to its host.
How does the immune system respond to disease?
- White blood cells produce antibodies that stick to pathogens- Phagocytes then ingest the pathogens- Lymphocytes release antibodies specific to the pathogen
How are vaccinations successful?
They manufacture memory cells that enable future antibody production to occur sooner, faster and in greater quantity
What do platelets do?
They aid in blood clotting
Why does our blood clot?
It prevents blood loss and the entry of potentially harmful microorganisms
Artery structure
- Thick wall (high blood pressure/oxygenated blood)- Elastic walls- Narrow lumen
Vein structure
- Thin wall (low blood pressure/deoxygenated blood)- Valves to prevent backflow- Wide lumen
Capillary structure
- Very thin wall (1 cell thick)- Very small lumen
What is an artery?
A blood vessel that carries blood away from the heart
What is a vein?
A blood vessel that carries blood to the heart
What is special about the pulmonary artery?
It is the only artery to carry deoxygenated blood.
What is special about the pulmonary vein?
It is the only vein to carry oxygenated blood.
Which chamber does blood first enter?
Right atrium
Which type of valve connects the atrium and ventricle?
Atrioventricular valve
Which type of valve is present in arteries leaving the heart?
Semilunar valve
Which blood vessel carries blood to the lungs for oxygenation?
Pulmonary artery
Which chamber of the heart sends blood to the aorta?
Left ventricle
Normal resting heart rate
60-100 bpm
Normal exercise heart rate
150-200 bpm
What are the five kingdoms?
- Plants- Animals- Fungi- Protoctista- Monera
What does photosynthesis do?
Photosynthesis uses sunlight to make glucose from carbon dioxide and water, with oxygen as a byproduct, also using chlorophyll.
How does carbon dioxide affect the rate of photosynthesis?
More carbon dioxide increases the rate of photosynthesis
How does light intensity affect the rate of photosynthesis?
Higher light intensity means more light energy can be converted to chemical energy, so it increases rate of photosynthesis
How does light colour affect the rate of photosynthesis?
Photosynthesis doesn't work well in green light (it is reflected by the green leaves).
How does temperature affect the rate of photosynthesis?
Photosynthesis has an optimal temperature in different plants, because it is catalysed by enzymes.
What does the xylem transport?
Water and mineral salts (from the roots to the leaves)
What makes up the walls of the xylem?
The walls of xylem are made of dead cells. They have lignin molecules.
What does the phloem transport?
Glucose (away from the leaves and to parts of the plant that can't photosynthesise), sucrose and amino acids.
What are the three ways substances can move into and out of cells?
DiffusionOsmosisActive transport
What is transpiration?
The evaporation of water from the surface of a plant.
Name the limiting factors that affect the rate of transpiration.
HumidityWind speedTemperatureLight intensity
How does humidity affect transpiration?
When the air is more humid, it is harder for the water to evaporate into the air. (More humidity = less transpiration)
How does wind speed affect the rate of transpiration?
The air around the stomata gets humid when transpiring, so the wind blows away the humid air. (Higher wind speed = more transpiration)
How does temperature affect transpiration?
An increase in the air temperature warms the water inside the leaves more quickly causing it to evaporate quicker.
How does light intensity affect transpiration?
In light, guard cells take up water by osmosis and become turgid. Because their inner walls are rigid they are pulled apart, opening the pore. In darkness water is lost and the inner walls move together closing the pore.Because of this, the transpiration rate is increased by an increase in light intensity.
What piece of apparatus can be used to measure the rate of transpiration?
A potometer (bubble potometer)
How do glasshouses affect the yield of crops?
Light can be turned on in the dark, making photosynthesis happen all the timeCOâ can be monitored and pumped through to increase the rate of photosynthesisTemperature can be controlledWind speed can be controlledHeating can increase the rate of photosynthesis
What is the alternative to a glasshouse?
Polythene tunnel
What substance(s) do plants require for growth?
Mineral ions
Which ions are needed for chlorophyll?
Magnesium ions
Which ions are needed for amino acids?
Nitrate ions
How does fertiliser increase crop yield?
Fertilisers provide plants with the essential chemical elements needed for growth particularly nitrogen, phosphorus and potassium.
Which chemical process is used to synthesise fertilisers?
The Haber-Bosch Process
Reasons for pest control
Pesticides are used to control various pests and disease carriers, such as mosquitoes, ticks, rats and mice. Pesticides are used in agriculture to control weeds, insect infestation and diseases.
Advantages of using pesticides
+ Prevent harmful insects damaging crops+ Kill pests faster than other pest control methods+ Easy to use+ Wide range available
Disadvantages of using pesticides
- Overuse can cause resistance- Kill beneficial insects (bees, wasps etc.)- Toxic to humans and animals- Can damage ecosystems and food chains- Diminish biodiversity- Reduce nitrogen fixation- Can destroy food-bearing plants
What is biological control of pests?
Biological control is the beneficial action of parasites, pathogens, and predators in managing pests and their damage.
Advantages of biological control
+ Cost effective (never runs out, one time investment)+ Safe for animals and humans+ Preserves food chains+ Does not affect fruit made
Disadvantages of biological control
- Predator can turn and eat the crops also- Slow process- Can't eradicate all the pests (predators only survive by having food to eat.)- Expensive starting costs- Can sometimes fail in specificity
Thin protective membrane that covers the front of the eye and lines the inside of the eyelids
Conjunctiva
Cells present in the retina that react to light, producing impulses in sensory neurones. They work only in bright light and can respond to different colours of light
red, green and blue. They produce a sharp image. -Cones
A small depression in the centre of the retina where a high concentration of cone cells can be found
Fovea
Muscle in the eye that relaxes or contracts to enable the lens to change shape for focussing
Ciliary muscles
A series of fibres that hold the lens of the eye in place
Suspensory ligaments
When light is bent. For example in the human eye at the air/cornea boundary and again at the lens
Refraction
When the pupil of the eye becomes smaller e.g. in response to bright light
Pupil constriction
The changes that take place in the eye which allow us to see objects at different distances
another word for focusing. -Accommodation
When a person focuses on a distant object the lens is ...............
Thin and flattened, less convex
When a person focuses on a nearby object the lens is ...............
Rounded, more convex
Inheritance
Transfer of features from one generation to another.
Chromosome
Supercolied thread of DNA wrapped around a scaffold of proteins.
Gene
Sequence of DNA that codes for a single protein.
Diploid
A cell containing two sets of chromosomes separately inherited from each parent.
Three examples of human proteins
Haemoglobin, Amylase, and Lipase.
Mitosis
Division of cells to create genetically identical daughter cells. Used in growth and asexual reproduction.
Meiosis
Division of cells that halves the number of chromosomes in cells (from diploid to haploid). Used to make gametes.
Allele
A version of a gene.
Homozygous
Two identical alleles of a gene (TT,tt).
Heterozygous
Two different alleles of a gene (Tt, tT).
Dominant allele
Allele that can determine the phenotype in a heterozygous individual.
Recessive allele
Allele that determines the phenotype only in homozygous individuals.
Genotype
The combination of alleles carried by an organism.
Phenotype
The appearance of an organism due to genotype together with interaction with its environment.
Bases found in DNA
Adenine, Thymine, Cytosine and Guanine.
Double Helix
The shape of a DNA molecule.
Gamete
Sex cells e.g. sperm or egg in humans.
Zygote
A fertilised egg cell.
Nucleus
Where the DNA is located in a cell.
Mutation
A change in the DNA content of a cell.
Homologous pair
A pair of chromosomes of similar length and banding pattern: one from the mother and one from the father.
What is a flaccid cell
When water has moved out of a plant cell by osmosis from an area of high to low water potential. The cell wall is touching the cell membrane but not exerting any force upon it.
Plasmolysed cell
When so much water has left the plant cell by osmosis that the cell membrane peels away from the cell wall.
Hypertonic solution
When a solution has a lower water potential than another solution.(more concentrated)
Hypotonic solution
When a solution has a higher water potential than another solution.(more dilute)
Isotonic solution
When two solutions have the same water potential.
Lose water by osmosis
Would plant cells immersed in hypertonic solutions gain or lose water by osmosis?
Gain water by osmosis
Would plant cells immersed in hypotonic solutions gain or lose water by osmosis?
Pathogen
A micro-organism that causes an infectious disease
Transmission
Passing a pathogen to an uninfected person
Transmissible disease
A disease in which the pathogen can be passed from one host to another
Vector
An organism that carries a pathogen from one host to another
Immune system
The body's internal defence system
Immune
Able to fight off a particular pathogen before it causes any symptoms in the body
Phagocytes
White blood cells that surround, engulf and digest pathogens
Lymphocytes
White blood cells that produce and release antibodies
Memory cells
Cells produced by active lymphocytes that remain in the body and are able to respond quickly to a pathogen
Antigens
Chemicals on the surfaces of pathogens which are recognised as foreign by the body
Antibodies
Chemicals secreted by lymphocytes which attach to antigens and help to destroy them
Antibiotic
A drug that kills bacteria in the human body without killing human cells
Penicillin
An antibiotic which destroys bacteria by damaging their cell walls
Auto-immune disease
A disease caused by a person's own immune system attacking parts of their body
Vaccination
Introduction to the body of dead or weakened pathogens to make a person immune to an infectious disease
Active immunity
Defence against a pathogen by antibody production
Passive immunity
Short term defence against a pathogen by antibodies acquired from another individual
Stimulus
A change in an organism's environment that can be detected.
Response
The way an organism reacts to a stimulus.
Transduction
When energy is changed from one form to another e.g. from light energy to electrical energy in the photoreceptors in the eye
Central Nervous System (CNS)
Consists of the brain and spinal cord
Reflex action
A rapid automatic (or involuntary) action in response to a stimulus that does not involve the brain
Reflex arc
The nerve pathway of a reflex:Stimulus > receptor > sensory neurone > CNS > relay neurone > motor neurone > effector > response
Dorsal root
Where all sensory neurones enter the central nervous system
Ventral root
Where all motor neurones emerge from the spinal cord
Dorsal root ganglion
A swelling in the dorsal root where the cell bodies of sensory neurones are located
White matter
Composed mainly of myelinated nerve cells. Forms the outer part of the spinal cord.
Grey matter
Composed of mainly nerve cell bodies. Forms the middle part of the spinal cord and the outside of the brain.
Sensory neurone
A neurone conducting impulses from receptors to the brain or spinal cord
Motor neurone
A neurone transmitting impulses from the brain or spinal cord to a muscle or gland
Axon
The long threadlike part of a nerve cell that carries impulses away from the cell body.
Myelin sheath
Fatty insulation that surrounds axons and helps to speed up the conduction of nerve impulses
Dendrons
The fine cytoplasmic extensions of a nerve cell body
Synapse
A junction between two nerve cells
Nerve-muscle junction
A special type of synapse where nerve endings from an axon connect with a muscle
Neurotransmitter
A chemical substance released from a nerve cell, allowing an impulse to travel from a nerve cell to the next.
Pituitary gland
Located at the base of the brain. It secretes a number of different hormones into the blood, including FSH, LH and ADH.
Hypothalamus
A region of the brain that coordinates the activity of the pituitary gland. It contains thermoreceptors and osmoreceptors involved in homeostasis.
Hormone
Chemical messenger released into the blood stream by an endocrine gland that causes an effect in a target tissue elsewhere in the body.
What is aerobic respiration
A series of reactions in cells that releases energy from glucose using oxygen
What is anaerobic respiration
A form of respiration that can occur without using oxygen. In this reaction glucose is not completely broken down and less energy is released e.g. in yeast and muscle cells
Oxygen debt
The volume of oxygen needed to completely break down the lactic acid build up produced in the body during anaerobic respiration
Lactic acid
Produced in muscles when glucose is respired anaerobically during strenuous muscular activity
Ventilation
The mechanism that moves air into and out of the lungs. Also known as breathing
Gas Exchange System
The lungs and associated structures make up this organ system
Thorax
The part of the human body between the neck and the abdomen, partially enclosed by the ribs and containing the heart and lungs
Diaphragm
A shallow dome-shaped, muscle that separates the thorax from the abdomen. Contracts when breathing in.
Trachea
A tube reinforced by rings of cartilage, that carries air from the larynx to the two bronchi
Bronchi
Tubes leading from the trachea into each lung
Alveoli
Microscopic air sacs found at the end of bronchioles. They have a large surface area to allow efficient gas exchange with the blood
Cartilage
Tough connective tissue found in the walls of the trachea and bronchi. It supports the airways and keeps them open when we breathe
Intercostal muscles
Muscles found between each rib
Pleural membranes
Thin, moist membranes that form a continuous envelope around the lungs, creating an airtight seal
Pleural cavity
Body cavity that surrounds the lungs
Pleural fluid
Acts as lubrication to ensure the surfaces of the lungs don't stick to the inside of the chest wall when we breathe
Mucus
Secreted into respiratory airways by goblet cells to trap particles of dirt and bacteria that are breathed into the body
Cilia
Fine hair-like projections that line the respiratory tract. They beat rhythmically to sweep mucus and trapped particles towards the mouth and away from the lungs preventing infection
Inhalation
Air is drawn into the lungs when external intercostals contract pulling the ribs up and out. The diaphragm muscles contract causing the diaphragm to flatten. This increases the volume in the thorax and lowers pressure inside so air is drawn into the lungs.
Exhalation
Air is forced out of the lungs when internal intercostals contract pulling the ribs down and in. The diaphragm muscles relax and the diaphragm returns to a dome shape. This reduces the thorax volume and raises pressure inside so air is forced out of the lungs.
A toxic gas present in cigarette smoke. It binds irreversibly with haemoglobin (forming carboxyhaemoglobin), preventing it from carrying oxygen.
Carbon Monoxide
A compound formed when haemoglobin combines with carbon monoxide in preference to oxygen
Carboxyhaemoglobin
Homeostasis
Maintenance of constant internal environment in the body despite changes in the external conditions.
Receptor
A cell that can detect a stimulus (eg photoreceptors in the eye detect changing light intensity)
Effector
Muscle which carries out a response (eg biceps contracting to lift an arm away from a hot object)
Endocrine system
Hormones (signalling molecules) transmit information around the body by travelling in the bloodstream to different organs.
Central nervous system
Brain and spinal cord
Reflex arc
Stimulus --> Receptor --> Sensory neurone --> Relay neurone (in the spinal cord) --> Motor neurone
Sweating
Releasing water and salts through sweat glands in the skin when the body gets too warm.
Vasoconstriction
Arterioles supplying the capillaries near the skins surface get narrower to reduce blood flow to the surface reducing heat loss
Vasodilation
Arterioles supplying the capillaries near the skins surface get wider to increase blood flow to the surface to increase heat loss
ADH
Hormone involved in regulating blood water potential released from the pituitary gland
Adrenaline
Hormone involved in the "fight or flight" response released from the adrenal glands
Insulin
Hormone involved in regulating blood sugar levels released from the pancreas
Testosterone
Hormone involved in male reproductive function released from the testes