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Biology

Coda templates

Syllabus

removed

2.5 - 2.6 stem cells

2.14 enzyme practical

2.33 food energy practical

2.40 - 2.45 plant gas exchange

2.53 - 2.58 plant transport

2.63 - 2.64 vaccination and clotting in detail

2.70 - 2.79 excretion and the kidney

2.81 homeostasis

2.86 hormone vs. nerves

2.95 ADH, LH, FSH

3.1 - 3.7 plant reproduction

2.86, 2.89, 2.91 - 2.94 Nervous system

4.1 - 4.5 biodiversity and field work

5.12 - 5.20 food production, selective

breeding, GM, cloning

1.1 - 1.4 variety and characteristics of life

2.1- 2.4 cells

2.7 - 2.13 molecules

2.15 - 2.17 movement in and out of cells

2.18 - 2.23 photosynthesis

2.24 - 2.32 diet and digestion

2.34 - 2.39 respiration

2.46 - 2.50 breathing and gas ex.

2.51 - 2.52 principles of transport

2.59 - 2.62 blood

2.65 - 2.69 heart and circulation

2.80 - 2.82 response to stimulation

2.83 - 2.85 plant tropisms

2.87, 2.88, 2.90 - 2.94 Nervous system

3.8 - 3.13 human reproduction

3.14 - 3.39 inheritance and evolution

4.6 - 4.9 food chains

4.10 - 4.11 carbon and nitrogen cycles

4.12 - 4.18 pollution

Breathing and Gas Exchange

Name and describe all the organs

1. Larynx, trachea and rings of Cartilage

protects lower airways. where air goes through. rings of cartilage prevent the trachea from closing

2. Bronchi, Bronchioles and Alveoli

air splits through all these different pathways, the smallest being the alveoli, where gas exchange occurs

3. Pleural membranes and Pleural fluid

pleural membranes surround the lungs, and it’s protected from sticking into the ribcage by the pleural fluid surrounding them

4. Diaphragm, intercostal muscles and ribs

Diaphragm and intercostal muscles expand and contract to change the volume capacity of the lungs, causing breathing. the ribs protect the lungs from being damaged

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Understand the role of the intercostal muscles and the diaphragm in ventilation

BIDEC

Breathe In Diaphragm and External Contract

BODER

Breathe Our Diaphragm and External Relax

Alvioli Adaptations

1. moist, allows gas exchange to occur

2. number of them gives for more surface area

3. one cell thick, short distance for diffusion

4. good supply of blood and oxygen to maintain diffusion gradient

Effects of Exercise in breathing and the release of carbon dioxide

exercise means that more glucose needs to be used for energy, meaning there is a higher demand for oxygen to release the energy. Breathing rates increase to receive more oxygen, turning it into carbon dioxide through respiration. since respiration rates are higher, the release of carbon dioxide also increases

How to carry out an experiment about the release of CO2

breathe through a tube connecting two test tubes. lime water is placed in both. the test tube where air enters remains clear, while the test tube where air goes out turns cloudy - a positive result for the presence of carbon dioxide.

Effects of Smoking (4)

1. Increase of risk of pulmonary infections

tar damages the cilia and mucor. these two cells produce mucus to trap pathogens and sweep them down the the stomach to be killed by the acidity.

2. Emphysema

the breakdown of alveoli reduces surface area, thus making it harder for gas exchange to occur and obtain oxygen.

3. RISK OF CORONARY HEART DISEASE

carbon monoxide binds with the red blood cells, not allowing the oxygen to bind. heart rate increases to make up for the lack of oxygen, which can damage capillaries and increase the risk of coronary heart disease

4. CANCER

contains radioactive substances that increase the risk of mutations

Food and Digestion

Describe the digestive system

Mouth and Salivary Glands

teeth break down the food so it can be swallowed and increases surface area so it can be digested quicker. moist also helps it travel down the oesophagus

salivary glands secrete AMYLASE to break down starch

Oesophagus

tube through which the food travels, is elastic and contains muscles to push it downwards

Stomach, pancreas

stomach is very acidic, kills all pathogens, bacteria. pancreas secrete protease, an enzyme which digests protein, whose optimum PH is 2 due to its acidity

Gall Bladder, Duodenum (small intestine)

gall bladder produces bile, which neutralises the food from the stomach as it is acidic as it is alkaline. it also emulsifies fat into smaller droplets in order to increase surface area to make the enzymes work more quickly. Lipase and other enzymes are excreted from the pancreas

Ileum lining

containing villi, one cell thick lining in the ileum covered by microvilli in order to increase surface area. have blood capillaries inside to shorten the distance of the nutrients and the blood, then transferred into the entire body. also contain mitochondria to move and match the concentration gradient, facilitating diffusion through active transport

Large intestine and rectum

absorption of remaining water to create a solid feces of undigested material, then excreted through the rectum.

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Elements present in carbohydrates, proteins and lipids

hydrogen, carbon, OXYGEN for both carbs and lipids,

protein is made of amino acids » hydrogen, carbon, oxygen, nitrogen and sulfur

lipids » GLYCEROL AND FATTY ACIDS

Tests for Starch, Glucose, Protein, Lipids

Starch

add iodine, initially orange, later turns BLUE BLACK

Glucose

add BENEDICT SOLUTION, from blue to BRICK RED

Protein

add BIURET TEST, forming PURPLE

LIPID

add ETHANOL, forming a CLOUDY WHITE LAYER

Identify the sources and uses of carbs, lipids, proteins, vitamins A, B, C and D, mineral ions, water and dietary fibre

Carbs

used for obtaining energy, found in wheats

Protein

used for the growth and repair of tissues, found in animal products and beans

Lipids

used to store in the body? found in avocados and nuts

Vitamin A

used to prevent night blindness, helps with the retina. found in carrots

Vitamin B

used to prevent beri beri, found in meat and veggies

Vitamin C

used to prevent scurvy, found in fruits and vegetables.

Vitamin D

used to prevent rickets, source from sunlight

Iron

helps the hemoglobin bond with the oxygen in red blood cells, preventing anemia. found in meat

Calcium

helps preventing rickets and weak bones, found in dairy

Water

needed by many parts of the body, including the brain.

Dietary fibre

helps with digestion, cellulose and found in most plants

How is food moved through the gut

a process called peristalsis in the walls of the gut,

the longitudinal muscles (external ) and circular muscles (internal ) contact and expand in order to move food along the gut

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Coordination and Response

Understand how organisms are able to respond to their environment

through the nervous system: based on the brain, spinal chords and nerves that perceives and reacts to changes in the environment

What does a coordinated response look like and what is the central nervous system

stimuli » receptor neuron » COORDINATION CENTER » motor neuron » effector

KEY DEFINITIONS

stimulus: any perceivable change in the environment

receptor: organs in the body that are able to perceive the environment. eg skin, eyes, ears, nose, mouth

effector: muscles, organs that are able to move accordingly to respond to its environment

coordinating center (CNS): involves the brain and the spinal cord, where neurons fire

type of neurons:

- receptor neurons CONVERT STIMULI INTO AN ELECTRICAL IMPULSE

- motor neurons

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describe the function, structure and adaptation of a simple reflex arc.

adapted to make the response faster, automatic and protective, thus avoiding danger.

does not involve the coordination of the brain

stimulus » receptor neuron » relay neuron » motor neuron » effector

Blood and circulation

Why can unicellular organisms can rely on diffusion

they have a high surface area to volume ratio, meaning their nutrients can diffuse easily through the entire cell. larger beings have a low surface area to volume ratio, thus a need for a transport system, as diffusion is not efficient enough

The structure of the circulation and heart

double circulatory

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VEINS = from the body to the heart

ARTERY = from the heart to the body

involving:

- pulmonary artery and vein

- vena cava and aorta,

- renal artery and vein

- hepatic artery and vein

Heart contains:

1. two ventricles (bottom)

2. two atria (top)

(4 chambers)

3. Valves

CARDIAC MUSCLE contracts and expands in order to pump the heart.

Factors that may cause Coronary heart disease

1. smoking

2. lack of exercise

3. hereditary and genetic

4. stress

5. diet

6. high blood pressure

Effect on heart rate of adrenaline and exercise

exercise demands more oxygen for the muscles in order to break down the glucose for energy.

the heart will have to obtain oxygen by the lungs at a faster rate, thus raising heart beat.

secretion of adrenaline for the adrenal glands also causes a quicker fast rate, as it helps the body be prepared for a fight of flight response.

controlled by the MEDULLA

How the structure of capillaries, arteries and veins relate to their function

Arteries

thick muscle and elastic tissue

to stretch and recoil to support high blood pressures. to control the blood flow by widening or contricting

Veins

thin muscle and elastic tissue, containing valves

no need for thick muscles due to low blood pressure, valves prevent it from going backwards

Capillaries

one cell thick

provides a very short distance for diffusion as it is close to every cell in an organ

Describe the Composition of Blood

1. Plasma

Liquid part of the blood: carries nutrients, other blood components, urea, hormones, HEAT

2. Red Blood cells

carry oxygen. adaptations:

- small, can squeeze through tiny capillaries

- hemoglobin binds with the oxygen to form oxyhemoglobin

- no nucleus gives more space for the hemoglobin

- biconcave shape, squeeze

3. White blood cells

designed to eliminate pathogens and protect the body

4. Platelets

parts of other cells that are broken, serve to close open wounds. Blood clotting: prevents blood loss and entrance of pathogens.

How does the immune system respond to infection using white blood cells and how do vaccines work.

1. two types of white blood cells: Lymphocytes and Phagocytes.

2. Phagocytes change their structure in order to surround and digest the pathogen

3. lymphocytes produce antigens to bond with the pathogen’s antibody.

it can take several days for the lymphocytes to find or produce the correct antigen to the specific antibody.

once it’s found the lymphocytes reproduce rapidly. also produces memory cells.

on a second infection of the same pathogen, the white blood cells will be able to eliminate all of them at a much faster rate and a greater quantity

Vaccines give a weak or dead version of a pathogen that won’t cause a lot of damage. The white blood cells are forced to produce antigens and memory cells, a process that may take several days. Once the body comes into contact with the real pathogen, the lymphocytes will produce the antigens at a faster rate and greater quantity.

Reproduction in Humans

Difference between sexual and asexual reproduction

sexual reproduction involves the fusion of a female gamete with a male gamete

asexual reproduction does not involve the fusion of a female gamete and a male gamete

Define Fertilization

the fusion of the female gamete nucleus with the male gamete nucleus to produce a zygote

The zygote then undergoes cell division through mitosis to produce an embryo

The structure of the male and female reproductive system.

· MALE

testis

where sperm is produced

sperm duct

muscular tube where the spect travels from the testis towards the urthera

uthera and glands

where sperm travels from the sperm duct towards the penus

the glands secrete liquid that is added to the sperm to produce semen

erectile tissue, penus, foreskin

erectile tissue swells with blood to make the penus erect

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· FEMALE

vulva and vagina

where the sperm is deposited

cervix

the neck of the uterus

uterus / womb

where the baby begins to be produced.

Endometrium and Muscular uterus wall

endometrium is the lining of the uterus, with good blood supply in order and stretchy to host the baby

Muscular uterus wall

Oviduct and ovaries

ovaries produce female gametes every 28 days

these travel down the fallopian tube (oviduct), where it meets with the male gamete to fuse. If fusion happens, it will be implanted in the endometrium

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Name the secondary sexual characteristics

FEMALE

- growth of breasts

- pubic hair and armpit hair

- widening of hips

- periods

MALE

- enlargement of penus

- pubic, armit and facial hair

- muscular

- deepening of voice

Describe the menstrual Cycle

Ovulation is the release of ripe female gamete (egg) from the ovary

1. FSH

produced in the pituitary gland

triggers the development of the egg in the ovary

triggers the production of Oestrogen in the ovaries

2. Oestrogen

triggers the thickening of the lining of the ovary

triggers the pituitary gland to stop producing FSH

triggers the production of LH

3. LH

triggers the release of the egg into the oviduct (DAY 14)

triggers the production of progesterone in the ovary

the male and female gamete will fuse 1/3 into the oviduct

4. Progesterone

maintains the lining of the ovary thick in case the zygote needs to be implanted

stops the pituitary gland from producing more LH and FSH

falls if there is no fertilization. the fall in progesterone and oestrogen levels causes the lining of the uterus to break, thus causing a period.

if fertilization occurs, the placenta will maintain the production of progesterone and oestrogen

Explain the role of the placenta in pregnancy

placenta: an organ that develops during pregnancy in order to provide nutrients and oxygen to the baby

gametes » zygote » embryo » fetus

thousands of cells in the ovaries are potential eggs. FSH triggers the development of one of these eggs into a Follicle

adaptations

1. increased surface area by villi

2. the maternal blood never comes into contact with the baby’s blood (it is dangerous because the mother’s body may interpret the baby’s blood as a pathogen, thus killing it)

3. the embryo is protected by AMNIOTIC FLUID surrounded by AMION MEMBRANE to prevent the contact between the blood of the baby and the blood of the mother and protects against bumbs

4. good supply of the maternal blood keeps the concentration gradient (nutrients, exchange of urea, co2 and o2 in the umbilical chord

UMBILICAL VEIN

away from the mother’s heart, towards the baby, carries the oxygen and nutrient rich blood

UMBILICAL ARTERY

towards the mothers heard, away from the baby, carries urea and co2

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Plants and Food

Required Practical: testing for production of starch

KEY POINT:

carbon dioxide + water » glucose + oxygen

1. place leaf in boiling ethanol to remove the chlorophyll

2. wash in cold water to soften

3. add iodine, blue black colour tests positive

note this will only work if the plant has had the chance to photosynthesise, thus it must have had some hours of sunlight before the test.

Required practical: investigate the need for light, carbon dioxide, chlorophyll and water FOR PHOTOSYNTHESIS

INVESTIGATING THE NEED FOR LIGHT

1. set the plant in a dark room for some days

2. test for starch with iodine

plants need light, so iodine will test negative for presence of starch.

INVESTIGATING THE NEED FOR CARBON DIOXIDE

1. set the plant in a closed bell jar with sunlight, water and all other control variable

2. place soda lime in the bell jar (it absorbs all the carbon dioxide)

3. test for starch

INVESTIGATING THE NEED FOR CHLOROPHYLL

1. the same test as for starch: removing the chlorophyll using boiling ethanol and leaving the plant for a few days will mean it will not be able to produce stach

INVESTIGATING THE NEED FOR WATER

1. give the plant an isotope of oxygen in water (H2O)

2. “track” the isotope to see if it appears in the photosynthesis products

we can’t deprive a plant from water, because it is needed for many other functions other than photosynthesis so it will die.

Required practical: test for oxygen as a product of photosynthesis

1. set an underwater plant on a beaker full of water.

2. collect the gas with a test tube

3. test the gas for oxygen using a glowing splint

Note: this practical can also be used to investigate the rate of photosynthesis at different light intensities.

Word and Symbol equation for photosynthesis

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Describe the structure of the leaf and its adaptations for photosynthesis

1. Cuticle

waxy layer on the top section of the plant. prevents any water loss EVAPOTRANSPIRATION and acts as a barrier to pathogens

2. Upper Epidermis

contains few or no stoma. is also relatively transparent to allow the palisade to receive sunlight

3. PALISADE CELLS

contains lots of chlorophyll to photosynthesise, is found in the upper section of the leaf to receive sunlight

4. SPONGY CELLS

form gaps of air where gas exchange happens

Note: MESOPHYLL LAYER IS MADE OF THE PALISADE AND SPONGY CELLS

5. LOWER EPIDERMIS

site of gas exchange. contains important cells of STOMATA and GUARD CELLS, which changes its shape to open and close to prevent the water loss.

6. XYLEM AND PHLOEM

xylem transports water and minerals from the roots, forming part of the transpiration system.

phloem transports the products such as sugars

correlation between gas exchange and photosynthesis and TEST FOR CO2 CONCENTRATION (triple only)

respiration occurs constantly

photosynthesis occurs at certain times.

if photosynthesis rates are higher than respiration (midday sunlight) , the pant will we uptaking more carbon dioxide than oxygen

is respiration rates are higher than photosynthesis (midnight darkness), the plant will not be producing oxygen, so co2 levels will rise.

test: hydrogen carbonate reacts will co2. high concentration is yellow, normal concentration is orange and low concentration is purple. set three test tubes with different light intensities with hydrogen carbonate

Factors affecting photosynthesis

1. light intensity

2. concentration of co2

3. temperatures

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why isn’t the curve linear? the plant’s photosynthesis rate increases as you give them their optimum temp, light intensity ect. but stop increasing as they have another LIMITING FACTOR

Mineral ions needed in the soil

Magnesium to make chlorophyll

nitrate ions to make amino acids (protein)

Transport in plants (2.15 and 2.17 only)

define diffusion, osmosis and active transport

Diffusion: the net movement of particles from high to low concentration

Osmosis: the net movement of water particles from high concentration to low concentration through a partially permeable membrane

Active Transport: the net movement of particles from LOW TO HIGH concentration which requires energy from the organism (eg. transport in the ileum)

Factors affecting diffusion

1. concentration gradient (higher means quicker)

2. distance

3. heat.

4. Surface area to volume ration

Required practical: investigating osmosis

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Plant Tropisms

Tropism : a response to a stimulus

A positive tropism in which the response goes TOWARDS the stimulus A negative tropism in which the response goes AWAY from the stimulus

Auxin is a hormone which responds to stimulus with growth in the tip of the coleoptile

Phototropism A response to light. plant moves towards the light in order to increase photosynthesis. The plant contains photo receptors, the auxin gathers in the opposite side to the light. Auxin makes the cellulose (a cage that inhibits growth) very loose. this stimulates growth.

Geo tropism A response to gravity, in the roots, towards the stimulus, a positive tropism. In the coleoptile, it grows away from the stimulus, a negative tropism.

Practice Question : Explain plant responses to stimuli

Tropism is a response to a stimulus. Auxin is responsible for responding to stimuli

Phototropism is a response to light. If light comes through only once side, the light receptors in the plant allow for the auxin to accumulate in the opposite side to light in the coleoptile, the tip of the plant's shoot. Auxin stimulates growth, as it makes the plant cell wall, the cellulose, loose and allows for growth. Over time this causes the plant to grow towards the light - a positive tropism

Geo tropism is a response to gravity. the roots grow towards gravity, as auxin accumulates in the underside. This occurs too

Why do some biologists not consider auxin a hormone?

it is not produces in a specific tissue

auxin is a trigger to pre set system, making different consequences it does not have a specific function

Plant growth substances stimulate root growth from a cut stem Describe an investigation to find the best concentration of plant growth substances to stimulate root growth.

CORMS

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Ecology and the environment

4.6 Trophic Levels

1. Producer: plants which photosynthesise to convert light to chemical energy (food)

2. Primary consumers: organism which feeds by the producer

3. Secondary consumer: organism which feeds by the primary consumer

4. Decomposer organisms which break down the dead material and help recycle nutrients

Food chains, food webs, pyramids of number, pyramids of biomass and pyramids of energy transfer

FOOD CHAINS

show the flow of energy from the sun to the last consumer.

Hence, arrows are pointing right »»»

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FOOD WEBS

a more detailed way to show an ecosystem and how energy flows

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PYRAMIDS OF NUMBER

they don’t have to be pyramid-shaped!! eg. a single tree may feed thousands of ladybugs

PYRAMIDS OF BIOMASS

are usually if not only pyramid-shaped

PYRAMIDS OF ENERGY

always pyramid shaped

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YOU MAY BE ASKED TO DRAW A PYRAMID

Transfer of energy along a food chain

only 10% of the energy is transferred along each trophic level

why?

1. heat loss or energy loss

2. energy transferred to make non digestible material (such as bones)

3. not all the energy from the food is absorbed (feces)

4. not all is eaten

this is why most of the food chains are 3-4 organisms long:

if plants are 100% of the energy, this transfers to 10% » 1% » 0.1%

animals who are tertiary consumers don’t obtain much energy

Draw the Carbon cycle

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photosynthesis fixes carbon into organic molecules such as carbohydrates

these are eaten by animals and other organisms which respire them.

carbon in dead organisms is broken down and released to the atmosphere again

fossilisation of plants and dead organisms are then burnt and released into the atmosphere again

note there is also an ocean uptake of the carbon

Draw the Nitrogen cycle (triple only)

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DECOMPOSERS (bacteria)

Nitrogen fixing

from the atmosphere to the soil

Denitrifying

from the soil to the atmosphere (a process called denitrification)

Nitrifying

turns AMMONIUM IONS into NITRATES which the plants use (a process called nitrification)

Decomposers

turns proteins into ammonium ions

consequences of pollution of air by sulfur and carbon dioxide

sulfur dioxide is acidic, causing acid rain

damages ecosystems, it changes the ph of lakes which can be fatal for organisms

damages infrastructure

makes soil infertile and damages the minerals, no more trees

carbon dioxide is a greenhouse gas, meaning it retains heat

although it is natural and essential to maintain heat during night time, its excess leads to global warming.

the melting of the arctic causes sea levels to rise

the melting of the antarctic does not cause sea levels to rise, but does extinct species such as the polar bear, seals and penguins

disrupts the carbon cycle

other greenhouse gasses and human activity

Water vapour

Carbon dioxide

Methane

Nitrous oxides

human activities leading to global warming:

burning fossil fuels

maintaining cows

mass production and no re/up cycling such as plastic, clothes

killing trees and plants (the only way that carbon is taken away from the atmosphere)

use of CFCs in refrigerators

nitrous oxides in fertilizers and car fuels, and sewage

biological consequences of water pollution sewage and fertilizers

is a good source of food for decomposing bacteria, so they reproduce quickly. they take up all the oxygen of the water, leaving none left for the rest of the animals, thus killing them.

EUTROPHICATION

occurs with both fertilizers and sewage

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effects of deforestation. (triple only )

1. LEACHING

deforestation means that trees don’t take up the nutrients and minerals. such minerals and nutrients are washed away by the rain, causing the soils to become infertile

2. SOIL EROSION

roots of the trees help prevent erosion from the rain in the soil

3. EVAPOTRANSPIRATION

no trees to evapotranspirate water vapour means less formation of clouds, thus less precipitation (rain)

4. CARBON CYCLE

disrupted - more carbon in the atmosphere

5. LACK OF BIODIVERSITY AND DISRUPTION OF ECOSYSTEMS

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Inheritance and Evolution

Chromosomes, Genes and DNA

Definitions and Locations for DNA, RNA, Genes, genome and Chromosomes

Genetic materia (DNA) is found in the nucleus of a cell

DNA:

a double helix structure containing the genetic information for all cells

two strands coiled to form a double helix, linked by the bases Adenine, (a) thymine (T), Cytosine (C) and GUANINE (G)

RNA:

single stranded containing uracil (U) instead of Thymine (T)

CHROMOSOME:

tightly packed dna. Humans have 23 pairs of chromosomes

GENES

section of the chromosome containing instructions for the production of particular proteins

alternate forms of the same gene are called alleles such as the gene coding for blue, brown eyes.

GENOME

the complete set of genetic material of an organism

Definitions diploid and haploid

Diploid » containing 23 pairs

Haploid » containing 23

all cells are diploid EXCEPT for gamete cells, which are haploid due to their division of Meoisis, which then fuse to create the 23 pairs.

Protein Synthesis

Describe the process of protein synthesis. (triple only)

Key points to remember:

DNA codes with CODONS which are triplets of the bases A adenine, T Thymine, G guanine and C cytosine

A and T are complimentary. G and C are complimentary

RNA is a single strand containing uracil U instead of T Thymine

Ribosomes are OUT of the nucleus

Protein synthesis is the process of reading the dna to convert it into amino acids

step one: TRANSCRIPTION

only occurs to sections of DNA at a time - a single gene at a time

takes place in the

rna polymerase (enzyme) binds just before the beginning of the gene

formation of Mrna (messenger RNA) which is complimentary to a strand of DNA, forming a single strand and replaces all the thymines with uracil

once the transcription is completed the rna polymerase detaches from the DNA, the Mrna is free to leave

step two: TRANSLATION

occurs in the ribosomes

produces a protein out of the sequence of amino acids

TRNA contains an anticodon, which is a sequence of triplets that are complimentary to the the MRNA, and an AMINO ACID

different TRNA’s bind with the MRNA, setting the amino acids in a specific order

once the sequence is complete the TRNA detaches and leaves a chain of amino acids behind.

Mutations

alteration of the DNA base sequence. this can happen in the dna or in the mrna (transcription) when it happens in the dna, it is likely to have a long lasting effect, as the wrong dna will be transcribed several times.

Amino acids sequences are very important in order to make 3D shapes to carry out their functions. Mutations can result in alterations in the amino acid sequence, resulting in the inability to complete its function

Single Base mutations

one base of the amino acid

mutations rarely cause an effect on the phenotype

however some do (eg. Cancer)

Types of errors during protein synthesis

Addition TAG CGA TTA TAG CCC GAT T

Deletion:

Mutagens: external factors that increase the likelihood of mutations

carcinogens (found in tobacco)

radiation (x rays, gamma rays, ultraviolet )

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Mitosis and Meiosis

Why do we need the division of cells?

growth and repair

production of specialized cells

sexual reproduction

genetic variation

Mitosis

each chromosome duplicates itself.

it then divides

genetically identical: the number of chromosomes is preserved from the original to the final one

occurs in every cell division except for the reproductive cells.

growth, repair, asexual reproduction and cloning

Meiosis

this is for the process of fertilization, hence it halves the number of chromosomes into 23 called a reduction division

cell division used for the formation of gametes (sex cells) produced in the testies and the ovaries

every chromosome makes a copy of itself.

right before the first division, there is a mixing of the DNA, to increase the genetic variation.

the fusion of dna of two different parents also promotes genetic variation

main difference: meiosis divides two times, and the division is not by a halve, but a division of "pairs" the separation of the copies occurs in the second division

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Genes and Inheritance

definitions: Heterozygous, Homozygous, allele, phenotype and genotype. (CODOMINANCE for triple only)

Phenotype

the physical characteristics (genes + environment)

most phenotype characteristics are a result of Polygenic inheritance, aka the result of several genes’ expressions. for example skin colour is controlled by several genes, while sex is only controlled by one.

Genotype

the genetic characteristics (only genes)

Allele

a variation of the same gene (Aa)

a dominant allele is one that will transfer into the phenotype (physical characteristics) if it is heterozygous and given a capital letter

while a recessive allele will not transfer into the phenotype unless homozygous, given a small letter

Heterozygous

two different alleles (AB)

Homozygous

two same alleles (AA)

homozygous dominant - have the same dominant allele

heterozygous recessive - have the same recessive allele

CODOMINANCE

pattern of inheritance where neither allele is is dominant, so both alleles are expressed

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Genetic diagram used for probability:

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Monohybrid vs Polihybrd

Family Pedigree diagrams.

⁠

questions involving pedigree diagrams will usually give information of recessive and dominant alleles necessary for a characteristic. EG, the question will say “the gene for polydactyly is recessive rr”

carriers of polydactyly are usually expressed as half a shade in the pedigree diagram . They contain the gene for polydactyly but it is not expressed, as it is recessive

people with polydactyly will be expressed as a full shade. they have homozygous recessive

people without any genes of polydactyly are white.

. The offspring inheritance can be deduced

calculating probability:

https://www.bbc.co.uk/bitesize/guides/z2rm3k7/revision/6⁠

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Determination of sex is in one of the chromosomes:

XX in a female, XY in a male

Natural Selection and Evolution

Explain Darwin’s theory of Natural Selection

process where certain individuals are more adapted and hence have more change of survival in a certain environment. thus, their genes are more likely to spread, resulting in a slow change of characteristics in a species of a specific environment

Understand how resistance to antibiotics an increase in bacterial populations

Antibiotica are chemicals that kill bacteria.

Resistance to an antibiotic first begins with a random mutation that causes the bacteria to be better adapted.

the new antibiotic-resistant bacteria is at an advantage to the other non-resistant bacteria, thus it is more likely to reproduce.

each offspring is born with the genetic variation that allows it to be resistant, thus reproducing even further, while the non resistant bacteria die

eventually all the bacteria from that species are resistant, and the antibiotic is no longer effective.

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