Biology iGCSE Notes

Página 1

Section 1

a)

Movement

Respiration

Sensitivity

Homeostasis

Growth

Reproduction

Excretion

Nutrition

The Kingdoms

Plants

Animals

Fungi

Bacteria

Protoctists (The waste men)

Plants - store carbohydrates as starch/sucrose

Animals - store carbohydrates as glycogen

Fungi - store carbohydrates as glycogen

Virus - Not a kingdom

Pathogen - A micro-organism that causes diseases

Can be fungi, bacteria, virus or protoctists

Página 2

Section 2

a) organelles - cells - tissues - organs - systems - (organism)

c) Biological molecules

Carbs = C,H,O

Proteins = C,H,O,N

Lipids = C,H,O

Carbs (starch or glycogen) - made from simple sugars (glucose & fructose)

Proteins - made from amino acids

Lipis - made from 1 glycerol molecule + 3 fatty acid molecules

Tests

Glucose - 4cm3 of sample + 1cm3 of Benedict's Solution in a test tube

Heat in a water bath at 50C for 2-3 mins

Turns light blue to brick red

Starch - 5cm3 of sample in a test tube

Add drops of Iodine solution

Turns golden brown to blue/black

Low temperature = Inactive enzyme. Substrate and enzyme collide less often

Optimum temperature = Lots of kinetic energy, colliding more and enzyme is most active

Over optimum temperature = Active site shape changes. No longer complementary to substrate. Enzyme denatures

pH - As it changes (high or low) the shape of the active site also changes ∴ less collisions successful

Experiment

Place separate boiling tubes with fixed volumes of starch and amylase into different temperature water baths

Wait 5 mins for solutions to reach temperature

Mix the starch and amylase and immediately do step 4

Every 1 min transfer a small sample using a pipette into a spotting tile well and add iodine solution. Will immediately turn blue/black

Record colour. When the iodine turns golden brown no starch is present because all the starch has been digested by enzymes.

Compare results to see at which temperature the iodine turned golden brown first. Rate = volume of starch/time taken to go golden brown

d) Osmosis, diffusion, active transport

Rate affected by SA:V ratio, temperature and concentration gradient

Plants cells are usually turgid because the cell wall is much stronger than the cell membrane. It keeps leaves firm and plant upright if it has no wood

Plant cells can plasmolyse & Animal cells can shrivel

Think : Hyper = lose energy = lose water

Remember - Iso/Hypo/Hyper tonic to the cell

e) Nutrition

Flowering Plants

magnesium ions - for chlorophyll

nitrate ions - for amino acids (to make protein)

Hydrogencarbonate indicator:

Yellow = High CO2

Orange = Normal CO2

Purple = Low CO2

h) Transport

Flowering Plants

Xylem - Water and minerals

Phloem - Sucrose and amino acids

More light so stomata open, so more water is lost

Humans

Hepatic artery/vein = Liver

Hepatic portal vein = Digestive system to liver

Renal artery/vein = Kidney

Pulmonary circuit - Heart to lungs

Systemic circuit - Heart to body

Double circulatory system: More efficient

Allows higher levels of activity as oxygen + glucose can be pumped to muscle cells quicker

Respiration needs to take place quickly to maintain body temperature of 37C

Single cell organisms have a high SA:V ratio so can supply the demand

Multicellular organisms have a low SA:V ratio. & skin does not allow much diffusion

i) Excretion

Flowering Plants

Excrete O2 and CO2 through stomata

Humans

The Kidney carries out excretion AND osmoregulation

Ultrafiltration in glomerulus. Glomerular filtarte is what gets past into the Bowman's Capsule

Selective reabsorption (uses active transport) in proximal convoluted tubule of glucose,amino acids and some water

Urine contains water,urea and salts

Negative feedback. ↓Little water - ↑ADH - Collecting duct permeability↑ - ↑ water reabsorbed in blood

Urinary system = Kidneys → Ureters → Bladder → Urethra

j) Co-ordination and response

Flowering Plants

Photo,Geo,Hydro tropism. +ve = towards, -ve = away the direction of stimulus.

Humans

Stimulis → receptor → coordination → effector → response

Accommodation - Focusing of the lens by the changing of its shape. (depending on object's distance)

First think of what the suspensor ligaments do (contract or relax), then remember the ciliary muscles do the opposite

ADH - Pituitary gland, permeability of collecting duct

Insulin/Glucagon - Pancreas. Change blood glucose level

Adrenaline - Adrenal glands. Fight or flight

Oestrogen/Progesterone - Ovaries. Regulates menstrual cycle/Secondary sexual characteristics

Testosterone - Testes. Secondary sexual characteristics

Página 3

Section 3

a) Reproduction

Flowering Plants

Asexual reproduction by runners (natural) and cuttings (artificial)

Germination needs O2, H2O and the correct temperature

Humans

Placenta allows. O2, Glucose, Minerals to diffuse, and amino acids by active transport M→F

CO2,Urea to diffuse, Water by osmosis F→M

Bloods don't mix as blood type could be different so mother's body sees it as a pathogen and kills it

Mother's blood pressure to high for the weak foetus

Placenta takes over from empty follicle and produces progesterone to maintain uterus lining

Amniotic fluid in amniotic sac protect foetus from bombs and jolts and keeps the temperature constant

b) Inheritance

Adenine - Thymine & Guanine - Cytosine

XX = Female, XY = Male

Mitosis - 2 identical diploid cells (occurs during growth,repair,closing,asexual reproduction)

Meiosis - 4 different haploid gametes (occurs during gamete formation)

Ionising radiation (gamma,X-rays, UV rays) & chemical mutagens (chemicals in tobacco) increase the incidence of mutations

Selection pressure,survival of the fittest,variation within the natural population, genes, inherited, beneficial mutation,rare/random,adaptation,evolution,reproduce/mate

Página 4

Section 4

a) The organism in the environment

Population - All the organisms of the same species living in an ecosystem at a particular time

Community - All the populations of different organisms interaction with their habitat

Habitat - A place where specific organisms live

Ecosystem - A community of organisms interacting with each other and their habitat/environment

Quadrats. Populations size - Count no. of species in square. Repeat and avg. Multiply avg. by area of field.

Quadrats. Distribution of organisms - Place quadrants in different locations. Compare the density/no. of species

b) Feeding Relationships

Only 10% of energy transferred because:

Some parts of the organism are not eaten (roots)

Some of the food is indigestible (Bones,cellulose)

Some of the food absorbed forms excretory products (urea)

Most of the food is used for respiration, movement, active transport. Little is left for growth or protein

c) Cycles

H2O - evapouration, transpiration, condensation, precipitation

C - respiration, photosynthesis, decomposition, combustion

d) Human influences on the environment

SO2 = Sulphuric acid. Acid rain (SO2 & NOx) = Acidification of water and sea ∴ kills aquatic life and trees, erodes limestone buildings

CO = Binds to haemoglobin. Asphyxiation

Greenhouse gases = Water vapour, CO2, nitrous oxides (NOx), Methane (CH4), CFCs (refrigerator coolants)

Global warming= Polar ice caps melt, Sea level rise, Changes in rainfall (drought/floods), Extinction of polar species

Deforestation = leaching, soil erosion, disturbance of water cycle (less transpiration, more drought/flooding), disturbances of the balance of O2 and CO2 in atmosphere (less trees & trees burnt)

Leached nitrates from fertilisers = algal blooms develop, sun blocked, plants die, ↓O2, fish die, (NO3 supply stops so algal blooms die), lots of decomposition by fungi/bacteria, Biological Oxygen Demand (BOD) ↑, everything dies. EUTROPHICATION

Sewage - Contains lots of bacteria/micro-organisms + nutrients, bacteria decompose sewage, bacteria respire, BOD ↑, fish die (∴ nutrients ↑,algal blooms, eutrophication)

Detergents,fertilisers and sewage can cause eutrophication

Página 5

Section 5

a) Food production

Pesticides : +ve = Very effective. Kill all the pests. -ve = Expensive, pests can become resistant, cause env. damage as some remain in soil and food chain, kills other organisms too

Biological control : +ve = Cheap. Self regulating as predator won't kill itself + reproduces. -ve = does not kill ALL the pests. Predator may enter the wild and affect biodiversity

CO2 production by yeast experiment - Add sucrose solution + oil layer (blocks air) andplace in different temp water baths. Collect Co2 over water in measuring cylinder to measure rate. Use limewater to test

Lactobacillus bulgaricus

Fermenter: aseptic conditions = Sterile. Filter air and sterilise the fermenter

Intraspecific predation - Fish of the same species eat each other. Separate different age, gender & feed often

Interspecific predation - different species eat the fish

b) Selective breeding

Selective breeding - Individuals

with desired

characteristics are bred together to produce offspring that express both

desired characteristics.

Plants - Higher yields, more nutritional to humans, resistant to diseases and pests, hardier to survive in harsher climates and conditions for longer year production

Animals - More meat/eggs/milk, more fur/higher quality fur, more offspring, resistant to diseases

c) Generic modification

Restriction enzymes - Cutting + Ligase enzymes - Sticking

Recombinant DNA - DNA from 2 different organisms that has been recombined

Transgenic Organism - The organism that receives the new gene from a different species

GM Plants are : Increased resistance to pests,pathogens,heat,drought, high salt. Extended shelf lives,contain more vitamins, higher yields, easier to eat/process

-ve = Could be more vulnerable to change in conditions or diseases as they are GM

d) Cloning

Micropropagation/tissue culture - Explants, Sterile, tissue culture, grown in vitro, clones, hormones + nutrients (optimum growing conditions), agar medium, controlled conditions (temp., light, humidity)

+ve = Large numbers produced rapidly, planted all year round, species that are hard to grow can be reproduced, GM only small no. of plants but then introduced into thousands quickly, plants can be stored easily

-ve = Plants could be vulnerable to change in conditions or a new disease

Dolly the Sheep - Diploid nucleus from body/stem/udder cell electrically zapped with enucleated egg cell, divided by mitosis to form an embryo, implanted into surrogate mother

transgenic animals - Can produce antigens of a specific bacteria/virus for vaccines given to people, grow human antigens on their organs for transplant as body is less likely to reject them, sheep produce milk with specific proteins for humans needed to treat diseases like cystic fibrosis