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Biology Year 9 Revision End of year - Coggle Diagram
Biology Year 9 Revision End of year
Variation, extinction and evolution
Evolution - the process by which living things change over time, over many generations
Simple life formed approximately 3 billion years ago.
Evolution occurs through a process of natural selection.
Charles Darwin - he suggests the theory of evolution by natural selection
He knew organisms had to compete for limited resources .
He concluded that organisms which had the most suitable characteristics for the environment would be more successful competitors and would more likely to survive. These are said to be well adapted.
Successful organisms would reproduce and pass the characteristics on.
Less well adapted would less likely to reproduce so not likely to pass on their gene
Benificial characteristics become common in population and species would change.
Evidence of Natural Selection
Fossils - These are preserved remains, impressions and traces of animals, plants or other living organisms millions of years ago. These are evidence of organisms which lived, they can show how much or how little organisms have changed, evolved, over time.
Ways which they can be formed:
Gradual replacement by minerals (most happen this way) - Things which don't decays easily, teeth, shells, bones etc. can last a long time when buried. When these decay they form a rock like substance shaped like the original hard part. Eventually someone digs it up.
Preservation - In amber and tar pits, there's no oxygen or moisture so decay microbes wont survive, which means it won't decay. In glaciers its too cold for decay microbes and peat bogs are too acidic for decay microbes.
Cast and impressions - Sometimes fossils are burried in a soft material like clay. Clay then hardens and when the fossil decays, the clay keeps the shape of the fossil. Things like footprints can leave a impression when pressed into these materials.
Antibiotic resistance - When they mutate, they become resistant to antibiotics. So when bacteria reproduces, it passes on the resistance which means that eventually the whole population of a bacteria would be resistant. This means that the living organism would pass the antibiotic resistance genes on.
Extinction - when no individuals of a species remain
Extinction can happen when:
A new disease kills them all.
They can't compete with a (new) species for food.
A new predator kills them all (e.g humans)
A catastrophic event happens to kill them all (e.g. volcanic explosion.
The environment changes too quickly (destruction of habitat)
Variation - is the different characteristics between individuals in a population.
Causes of variation:
Genetic causes - Differences in gene which the individual has inherited, from their parents, this is genetic variation
Environmental causes - Difference in environmental conditions which the individual has developed.
Mutation - these are changes to the sequence of DNA. Can be caused by environmental factors.
Mutations can make the individual better suited for its environment, which leads to natural selection.
Cell structure
What are cells
Unicellular - organisms which consists just a single cell such as bacteria.
Multicellular - organisms which consists multiple cells such as a human which contains more than 50 million cells.
Eukaryotic and Prokaryotic
Eukaryotic cells - these are cells which form animals and plants
Prokaryotic - these cells are form bacteria, they are 10 times smaller than eukaryotic cells
μm - micrometers (10,000x smaller than 1cm)
Animal cells (eukaryotic) - they contain
-Cell membrane
-Cytoplasm
-Nucleus
-Mitochondria
Ribosomes
Plant cells (eukaryotic) - they contain:
-Cell wall
-Cell membrane
-Cytoplasm
Nucleus
-Mitochondria
-Ribosomes
-Permanent vacuole
-Chloroplast
Bacteria cells (prokaryotic) - they contain:
-Cytoplasm
-Cell wall
-Ribosomes
-Plasmids, DNA
-Bacteria DNA
-Cell membrane
Cell Organelle Names and Functions
Mitochondria - Where most of the reactions for aerobic respiration and energy takes place.
Ribosomes - Where protein is made in the cell
Cell wall - Rigid structure made of cellulose to support and strengthen the cell to protect it.
Nucleus - Where all the DNA and genetic information is stored which controls the cell activities.
Cytoplasm - Where all the chemical reactions take place. Is a gel like substance.
Cell membrane - Controls what goes in and out of the cell and holds it together.
Vacuole - Contains cell sap which is a weak solution of salt and sugar to help keep the cell rigid.
Chloroplast - Where photosynthesis happens, it contain chlorophyll.
Cell Names and Functions
In plants
Xylem cell - Hollow to allow water to flow through them.
Phloem cells - Each tube has holes which allows sugars to be transported and distributed around where food is needed.
Root hair cell - Large surface area to absorb more water and minerals.
In Animals
Muscle cell - Contains lots of mitochondria to release energy that is used for contraction.
Red blood cell - A biconcave (shape of cell) to increase the surface area so more oxygen can be absorbed
Sperm cell - Long, has a tail to swim, contains lots of mitochondria to swim and enzymes at the head so it can penetrate the egg.
Egg cell - Lots of cytoplasm (nutrient) to provide to the embryo to grow.
Nerve cells - Long and thin to carry out electrical impulses throughout long distances.
Microscopes
Resolution - Ability to distinguish between two points
Magnification - To see smaller things bigger or in more detail.
Electron microscope - These use electrons instead of light to form a image. They have a higher magnification and resolution but can only view dead cells and is very expensive.
Light microscope - Lower magnification and resolution but can view living cells. Not as expensive as electron microscope.
Communicable diseases and development of drugs
How are diseases caused and what they are?
Pathogens cause diseases. They are microorganisms which infect and body and reproduce which may also make toxins which kill or damage body cells making you feel unwell.
Different types of pathogens:
Fungal - Single celled but some have a body made of hyphae. These can grow and penetrate human skin and surface of plants, causing diseases.
Can treat the disease using fungicides and by stripping the leaves which are affected. Then destroy the leaves so it can't spread further.
Rose black spot - On rose plants leaves, purple and black spots begin to develop and they can turn yellow and drop off, resulting in death of the plant also could mean photosynthesis can't happen so the plant can't grow well.
Protist - All eukaryotic. Some are parasites. Parasites live on or inside other organisms and can cause them damage. Often transferred by vector which doesn't even get the disease itself.
Malaria - Mosquito are the vector, they pick up the malarial protist when feeding on infected animal. When it feeds on other animals, it infects it by inserting the protist in the animal's blood. Repeated episodes of fever.
Stopping mosquitoes from breeding. Use insecticides and mosquito nets.
Viral - Not cells. They reproduce rapidly and uses/lives in your cell and replicate themselves using the cell to produce many copies. The cell would burst releasing the new virus and that is what makes you feel ill.
Tobacco mosaic virus - Affects plants. Causes mosaic pattern on leaves, parts of plant become discoloured , this means the plant can't carry out photosynthesis as well.
Getting vaccinated can stop most spread of viral diseases.
Measles - Spread from sneezing or coughing. Infected with it will result in red skin rash and signs of fever. Can be fatal, and sometimes lead to pneumonia (lung infection).
HIV - Spread from sexual contact or exchanging bodily fluids. Causes flu-like symptoms for a few weeks, then don't experience any for several years. Can be controlled with antiviral drugs which stop the replication.
Bacteria - They rapidly reproduce. They make you feel ill by producing toxins which damage you cells and tissues.
Bacterial disease can be treated with antibiotic drugs.
Salmonella - Causes food poisoning. Infected people can suffer fever, stomach cramps, vomiting and diarrhoea. You get it by eating food which has Salmonella bacteria. Most poultry (e.g. chicken) is given vaccination to stop the spread
Gonorrhea - Sexually transmitted disease. Pain when urinating or thick yellow or green discharge from vagina or penis. To stop the spread, we use antibiotics and barrier methods such as condoms.
How are they spread?
Food or water
Air
Exchange of body fluids
Direct contact
Vectors - An organism which carries a pathogen between other organisms. (e.g. insects)
Body defense systems
Non-specific defense systems (don't target specific pathogens)
Skin - Protects physical damage
Mucus - This is in your nose and they trap particles that could contain pathogens
Stomach - acid kills pathogen.
Specific defense system (white blood cells)
White blood cells - When some types of white blood cells come across an antigen which they don't recognize, they start to produce antibodies to lock onto the antigen so they can be found and destroyed.
Antigens come in different shapes ,meaning that the antibodies would have to be produced at a precise shape the same as the antigen.
Memory cells remember what the pathogen was and produce faster as there was the same antigen before, this makes the person feel less ill.
Antitoxin - They neutralize the toxins produced by the pathogen to make you feel less ill.
Phagocytosis - this is when the white blood cell engulfs the foreign cells
Vaccination and Medicine
Vaccine - Stimulates white blood cell to produce antibodies
Antibiotic - such as Penicillin are strong medicines used to treat bacterial infection. They kill or prevent the bacteria from reproducing in side the body. Can only use an specific antibiotic to that particular type of bacteria
Antibiotics cannot kill viruses or treat them, this is because the virus uses your body cells meaning it would be too difficult to kill it without damaging your body cells on the way.
A con of this is mutation of bacteria. This is when they mutate and become resistant to antibiotic. This means if used too much antibiotics, it would only kill the bacteria non-resistant and the resistant ones would be left meaning it would reproduce and become completely resistant.
To slow it down, you should avoid overusing antibiotics.
Drug development
Drug test
Toxicity - does the drug have any unwanted side effects?
Dose - how much of the drug should be given without causing harm?
Efficacy - How well the drug treats the illness?
Drug trials
Pre-clinical testing - tests on cells, tissues and live animals
Clinical testing - tests on healthy volunteers and patients, only used if passed pre-clinical.
Double blind trial - where the patient and doctor doesn't know that they are given the placebo or the real drug, this is to test the placebo effect.
Homeostasis and Endocrine system
Homeostasis - this is when the body maintains a stable internal environment in response to changes in the internal or external environment.
Negative feedback - this counter acts changes which keeps the internal environment stable.
If the level of something is too low, the receptor would detect it, CNS would organise a response and the effector would produce a response to increase the level.
If the level of something in the body is too high, the receptor would detect it, the CNS would organise a response and then it would be sent to the effector which counteracts the change and decreases the level
Many body conditions are maintained at their optimum level using Homeostasis, these include:
Blood glucose levels
Water levels
Core body temperature
Mineral ion levels
Hormones and endocrine system
The endocrine system is a collection of glands which secrete hormones
Endocrine glands:
Pancreas - Produces insulin which is used to regulate blood glucose level.
Ovaries (females) - Produce oestrogen which is used in menstrual cycle.
Thyroid gland - Produces thyroxine which regulates things like rate of metabolism, heart rate and temperature.
Testes (male) - Produce testosterone which controls puberty and sperm production
Pituitary gland - aka, 'Master Gland'. Produces many hormones to regulate body conditions. These hormones act on other glands directing them to release hormones that brind change.
Adrenal gland - Produces adrenaline which is used for 'fight or flight' responses.
Hormones are slower than nerves but last longer than nerves.
Adrenaline and Thyroxine
Adrenaline - prepares you for 'fight or flight'. Released by the adrenal gland which is just above the kidneys. This triggers a mechanism which increases the supply of oxygen and glucose to cells in muscles and the brain.
Thyroxine - released in the thyroid gland in the neck. Important role in regulating basal metabolic rate (speed of chemical reactions in body while at rest), it stimulates protein synthesis for growth and development.
Thyroxine is released in response to thyroid stimulating hormone (TSH) which is released from the pituitary gland. When level of thyroxine in blood is too high, the secretion (release) of TSH is stopped. This reduces amount of thyroxine so the level of blood falls back to normal.
Human Nervous System
Allows us to react to our surroundings and coordinate our behavior.
Nerves transmit electrical impulses around our body
Nerves contain many neuron, they carry electrical impulses between receptors, Central Nervous System (CNS) and effectors
The steps of the nervous system:
Stimulus
Sensory receptor
Coordinator
Effector
Response
1 more item...
Receive the information from CNS through the motor neurons.
Coordinator is CNS. It decides what to do. Then sends information to the muscle or glands
Receptors are the cells that detect stimuli. Sensory neurons carry information from receptor to CNS.
A change in surrounding, internal or external, which leads to a response.
Classification, genetic engineering and selective breeding
Classification - organising living organisms into groups
Carl Linnaeus classified all living things according to their characteristic into seven tier hierarchy:
Order
Family
Class
Genus
Phylum
Species
Kingdom
The more you go down the less organisms in each group.
Three domain groups - created by Carl Woese
Archaea
A different type of prokaryotic cell to bacteria, and were first found in extreme places such as hot springs and salt lakes.
Eukaryota
A broad range of organisms including fungi, plants, animals and protists.
Bacteria
Contains true bacteria. Although they look similar to the Archaea, there are lots of biochemical differences between them.
Genetic engineering - transfers genes between organisms
How is it done?
3) Using a different enzyme, stick the desired gene into the plasmid vector.
4) Put the vector into a suitable host, e.g bacteria.
2) Using the same enzyme, cut the plasmid vector which creates a space for the desired gene.
5) Allow it to reproduce making many copies of the gene.
1) The gene for the desired characteristic is isolated and cut out using enzymes.
6) Transfer into animals and plants at a early stage (embryo) so it developed with its desired gene.
GM (genetically modified) technology
Positives
Resistant to weed killers mean the farmer can spray the whole field without damaging the crops but just the weeds.
Saves quite a lot of time.
Being resistant to insects means it will not hinder/damage the growth of plants.
Faster growing plants if not affected by anything.
Negatives
Uncertain of long term health on humans if consuming GM crops.
May cause more allergic reactions because of altered DNA.
Population of wild flowers and insects may decrease if crops are successful.
Why is it necessary to transfer the desired gene at early stage?
So it ensure that all the cell of the organisms will contain the desired gene even when they divide.
Selective breeding - process where humans breed animals or plants to reproduce with the characteristics needed.
Examples:
Domestic dogs with gentle nature
Disease resistance in food crops
Animals produce more meat or milk
Process
Parents with the desired gene are chosen and bred together. Offspring breeds and then after many generations, the offspring show the desired gene.
Issues - inbreeding
When breeding people choose the "best" animals or plants which reduces the gene pool, this can cause health problems because there's more chance of the organism inheriting harmful genetic defects. e.g. pugs often have breathing problems.
Control of blood glucose
What causes blood glucose?
Eating causes blood glucose to go up
The pancreas secretes insulin in response to high blood glucose. This causes cells in the liver and muscle to take up the glucose from the blood.
When transported to the cells, it is stored as glycogen.
Excercise causes blood glucose to go down
If blood glucose becomes too low, the pancreas secretes a hormone called Glycogon, this regulates blood glucose by releasing the glucose stored in the liver.