Biology B1

Reflexes & Responding to Change

• Receptor detects stimulus (e.g. sharp pain)
• Sensory neuron transmits impulse to CNS
• Relay neuron passes impulse on to motor neuron
• Impulse passes to an effector (e.g. muscle/gland)
• The response happens

The CNS (central nervous system) consists of the brain and spinal chord. The 3 neurons (nerve cells) in order are sensory, relay and motor. Reflexes are rapid, automatic responses to a stimulus and happen without concious thought from the brain.

Hormones & The Menstrual Cycle

• FSH (follicle stimulating hormone) is made by the pituitary gland, causes the egg to mature and oestrogen to be produced
• Oestrogen is made by the ovaries, inhibits FSH, stimulates the womb lining to develop and the stimulates the production of LH
• LH (luteinising hormone) is made by the pituitary gland and stimuates the egg release (ovulation)

The menstrual cycle takes about 28 days with ovulation around 14 days into the cycle. The contraceptive pill contains oestrogen and progesterone as this prevents the production of FSH so no eggs can mature.

• Malnourished - the condition when the body does not get a balanced diet
• Metabolic Rate - the rate at which chemical reactions occur in the body
• Inherited - characteristic passed on from the parent to the offspring through genes
• Obese - very overweight, with a BMI of over 30
• Pathogen - disease causing microorganism
• Bacteria - single celled microorganisms that can reproduce very rapidly
• Virus - microorganism that takes over body cells and reproduces rapidly, causing disease
• White Blood Cells - blood cell that engulfs bacteria and makes antibodies to latch onto antigens and antitoxins to counteract toxins
• Immune System - the body system that recognises and destroys foreign cells or proteins
• Antibiotic - a drug that destroys bacteria inside the body without damaging cells
• Epidemic - when more cases of an infectious disease are recorded than normally expected
• Natural Selection - the process by which evolution takes place (only the fittest will survive as organisms produce more offspring than the environment support)
• Vaccine - dead or inactive pathogen used in a vaccination (which makes a person immune to that certain pathogen)

• Neuron - basic cell of the nervous system which carries minute electrical impulses
• Receptor - special sensory cell that detects changes in the environment
• Sensory Neuron - neuron which carries impulses from the sensory organs to the CNS
• Motor Neuron - neuron that carries impulses from the CNS to the effector organs
• Reflex - rapid, automatic response of the nervous system that does not involve any conscious thought
• Synapse - gap between neurons where information is passed on chemically
• Ovulation - the release of a mature egg from the ovary in the middle of the menstrual cycle
• Pituitary Gland - small gland in the brain
• Contraceptive Pill - a pill used to prevent conception
• Progesterone - female sex hormone used in contraceptive pills
• Internal Environment - the conditions inside the body
• Kidneys - organ which filters the blood and removes urea, excess salts and water
• Pancreas - organ that produces insulin and digestive enzymes
• Phototropism - the response of a plant to light (controlled by auxin)
• Gravitropism - response of a plant to the force of gravity (controlled by auxin)
• Insulin - hormone involved in the control of blood sugar levels

Controlling Conditions

The body controls:

• Water content - excess water is lost through urine, sweat and breath
• Ion content - excess ions are lost through sweat and urine
• Temperature - vasodilation and vasoconstriction, sweating, hairs stand up/stay flat
• Blood sugar levels - controlled by insulin

The human body temperature should be 37°C - if it gets too high, enzymes can denature.

Homeostasis - the maintainance of a constant internal environment.

Developing New Medicines

• First tests are in labs on cells and tissues or organs
• Then, the drug is tested on animals
• Healthy human volunteers tested on next
• Finally, patients are tested on

Drugs are tested to see if they work, if they are toxic, if they cause side effects and for the dosage.

Thalidomide was developed as a sleeping pill and was also initially used to cure morning sickness in pregnant women but then it led to limb deformities and other birth defects in the baby and it is now used to treat leprosy.

In a double-blind trial, neither the doctor nor the patient knows who is given the drug and who is given the placebo.

• Placebo - a substance used in clinical trials which does not contain any drugs at all
• Double-blind trial - a drug trial in which neither the doctor nor the patient knows if the patient is receiving the new drug or a placebo
• Thalidomide - a drug that caused deformities in the foetus when given to pregnant women to prevent morning sickness
• Statin - drug which lowers the blood cholesterol levels and improves the balance of HDLs to LDLs
• Depression - a mental illness that involves feelings of great sadness that interfere with everyday life
• Drug - a chemical which causes changes in the body (medical drugs cure disease or relieve symptoms and recreational drugs alter the state of your mind and/or body)
• Withdrawal symptom - the symptom experienced by a drug addict when they do not get the drug they are addicted to
• Steroid - drug that is used illegally by some athletes to improve performance and build muscles

Adaptation In Animals & Plants

In Animals:

• Thick fur and fat under the skin (blubber)
• Coat colour that changes in different seasons
• Bigger surface area to volume to help keep cool
• Smaller surface area to volume to conserve energy
• Hunt/feed at night to remain cool during the day

In Plants:

• Extensive root system
• Small waxy leaves
• Swollen stem to store water
• Thorns/poisonous chemicals
• Warning colours

Measuring Environmental Change

• Non-living factors which might change: temperature, rainfall, light levels, oxygen levels
• Living factors that might change: arrival of a new predator, disease, new plants that might provide new food/habitats

Lichens are a type of indicator species which have a higher population where there is less sulphur dioxide (the more lichens, the cleaner the air).

Freshwater invertebrates show how much water pollution there is and also the concentration of dissolved oxygen (the wider the range of invertebrates, the cleaner the water).

Rain gauges, thermometers, pH and oxygen sensors, data loggers can all be used to measure environmental change.

Changes in the environment affect the distribution of living organisms - e.g. birds may fly north if the climate gets warmer and so other birds may then have new competitors. The large fall in bee population may have been due to chemical sprays being used, a viral disease or changes in the flowering patterns of plants caused by climate change.

• Adaptation - special feature that makes an organism particularly well suited to the environment where it lives
• Herbivore - animal that feeds on plants
• Carnivore - animal that eats other animals
• Extremophile - organism that lives in environments that are very extreme e.g. very high or very low temperatures, high salt levels or high pressures
• Denature - change the shape of an enzyme so that it can no longer speed up a reaction
• Stomata - openings in the leaves of plants (particularly the underside) which allow gases to enter and exit the leaf, opened and closed by guard cells
• Competition - the process by which living organisms compete with each other for limited resources e.g. food, territory, a mate, light, etc.
• Territory - an area where an animal lives and feeds which it may mark out or defend against other animals
• Ovipositor - a pointed tube found in many female insects which is used to lay eggs
• Indictor Species - lichens or insects that are particularly sensitive to pollution and so can be used to indicate changes in environmental pollution levels

Decay Processes

• Decay process digests food or waste matter and recycles materials.
• Materials from living things decay because they are digested by microorganisms.
• These microorganisms cause decay by releasing enzymes that break down compounds to be absorbed by their cells.
• Bacteria and fungi are the main groups of decomposer.

Microorganisms are more active and digest materials faster when they are in moist, warm and aerobic conditions.

Processes which use materials must be balanced by those which release them.

Decay releases carbon dioxide as microorganisms respire.

• Biomass - biological material from living or recently living organisms
• Pyramid of biomass - a model of the mass of biological material in the organisms at each level of a food chain
• Solar energy - energy from the sun
• Urea - the waste product formed by the breakdown of excess amino acids in the liver
• Detritus feeder/Decomposer - microorganism that breaks down waste products and dead bodies
• Sewage treatment plant - a site where human waste is broken down using microorganisms
• Compost heap - a site where garden rubbish and kitchen waste are decomposed by microorganisms
• Carbon cycle - the cycling of carbon through the living and non-living world
• Combustion - the process of burning
• Organic waste - waste material from living organisms e.g. garden waste

• Chromosome - thread-like structure carrying the genetic information found in the nucleus of a cell
• Gene - a short section of DNA carrying genetic information
• Gamete - sex cell which has half the chromosome number or an ordinary cell
• Asexual reproduction - reproduction that involves only one individual with no fusing of gametes, it creates offspring that is genetically identical to the parent
• Sexual reproduction - reproduction which involves the fusion of male and female gametes producing genetic variety in the offspring
• Clone - offspring produced by asexual reproduction which is identical to its parent organism
• Tissue culture - using small groups of cells to make new plants
• Adult cell cloning - process in which the nucleus of an adult cell of one animal is fused with an empty egg from another animal, the embryo which results is planted into a third animal to develop
• Genetic engineering - a techique for changing the genetic information of a cell

Genetic Engineering

• A gene is 'cut' out of the chromosome of an organism using an enzyme
• The gene is then places in the chromosome of another organism

Genes can be transferred to the cells of animals and plants at an early stage in their development.

One gene controls one characteristc.

Genes may be placed in an organism of the same species to give it a 'desired' characteristic.

GM crops may be insect or herbicide resistant and usually have increased yields.

The gene to produce insulin in humans can be places in bacteria and then the bacteria can produce large amounts of insulin to treat diabetes.

Theories Of Evolution

• Lamarck suggested the theory of 'the inheritance if acquired characteristics'
• Darwin suggested the theory of natural selection, he did not know about genes

best adapted > survive > breed > pass on genes

Darwin's theory was only gradually accepted because the theory of natural selection challenged the idea that God made all the animals and plants on Earth and also because many scientists didn't believe there was enough evidence for the theory.

Darwin could also not explain why there was variety in organisms.

Scientists didn't know about genes back then.

Classification & Evolution

The main kingdoms are:

• Plant kingdom
• Animal kingdom
• Microorganism kingdom

The smallest group in the classification system is the species.

By putting organisms into groups, we can see how closely related they are (grouping organisms is called classification). They are classified by comparing similarities and differences.

Ecological relationships tell us how species have evolved together in an environment.

• Evolution - the process of slow change in living organisms over long periods of time as those best adapted to survive breed successfully
• Inheritance of acquired characteristics - Lamarck's theory on how evolution took place
• Jean-Baptiste Lamarck - French biologist who developed a theory of evolution based on the inheritance of acquired characteristics
• Charles Darwin - Victorian scientist who developed the theory of evolution by a process of natural selection
• Mutation - a change in the genetic material of an organism
• Natural classification system - classification system based on the similarities between different living organisms
• Kingdom - the highest group in the classification system
• Species - a group of organisms with many features in common which can breed successfully producing fertile offspring
• Evolutionary tree - model of the evolutionary relationships between different organisms based on their appearance and DNA evidence
• Evolutionary relationship - model of the relationships between organisms based often on DNA evidence which suggests how long ago they evolved away from each other and how closely related they are