Biology Blog

Adaptations

These are the FEATURE of an organism made to BEST SUIT it's ENVIRONMENT. If the environment changes, a species needs to adapt or it will become disadvantaged and probably extinct. Adaptations are caused by a mutation of the organism's genes. If the mutation is beneficial, then it will pass on the mutated gene to future generations, therefore evolving the species as this adaptation becomes the norm and other less beneficial version of the gene will die out.

When describing the adaptation don't forget to refer to WHAT in that HABITAT it is ADAPTING to

Variation

DIFFERENCES between members of the SAME SPRECIES are CONTROLLED by their GENES and/or the ENVIRONMENT. A good example to explain this is using identical twins, as they are from the same egg and sperm cell their DNA is exactly the same... Yet sometimes they are different. Take the picture to the left, the girls have different hair styles and one is taller, these differences must be environmental variations rather than genetic.

VARIATION come about by SEXUAL reproduction, this involves two parents COMBINING their GENES to give an offspring which is a MIXTURE of the two parents. The resulting combination is completely RANDOM. ASEXUAL reproduction however only involves one parent so the resulting offspring will be GENETICALLY IDENTICAL to the parent and therefore a CLONE.

Causes of variation - Genes, Environment or Both

Types of variation - Continuous or Discontinuous/Discrete

Predator Prey Relationship

There are usually more prey than predators, this is due to, larger predators needing many smaller prey to provide enough energy to keep them alive. As the population of prey goes up the predators population increases as food is more plentiful and there is LESS COMPETITION. If a population gets too large resources get used up due to MORE COMPETITION and organisms starve. Also a large population makes it easy for diseases to spead causing the population size to decrease. This pattern is on going, as shown by the graph above.

Evolution

Two names you will encounter are; Charles Darwin and Jean Baptiste Lamark. LAMARK used giraffe to explain his theory of evolution by saying that the shorter necked giraffe of the past, (Proven by fossil records) would physically stretch it's neck to reach the leaves on higher branches, thus giving them and their offspring longer necks. Therefore saying that parents can pass ENVIRONMENTAL variations on to their offspring (So why aren't baby's born with tattoos etc?) DARWIN however disagreed and said that there is variation among the short necked giraffes of the past, eg. some longer than others, would lead to them having an ADVANTAGE over the shorter necked giraffe.(They could reach more food.) This variation was due to the GENES they carried, as the shorter necked giraffe starved to death, their short neck genes died also. This lead to the longer, more benefical, long neck GENE SURVIVING to be PASSED on to the next generation.

Stages of Evolution

1.All members of a species are the same, showed no variation(eg giraffes necks same length).

2.A MUTATION occurs which gives that individual an advantage. (e.g. access more food, escape predators, resistant to poison or be more attractive)

3.The benificial mutation allows the individual to LIVE LONGER,

4.Reproduce more often, passing on the mutated GENE.

5.More are born with the benificial mutation, so out survive/compete the individuals without the mutated gene.

6.This is NATURAL SELECTION.

These stages are standard, to access more marks apply them to the question.

Some Rude Sounds Can Make Everyone Retch! You must know the order of events which bring about a response from a give stimulus. Stimuli include light, sound, chemicals which we can taste and smell, pressure and temperature. These are detected by receptors in the sence organs e.g. eyes, ears, tongue, nose and skin. Then an electrical impulse travels along a neurone to (Sensory) and from (Motor) the co-ordinator (CNS) to an effector, which is either a muscle or a gland this will bring about a response.

Health

Healthy living is needed for a longer life as it can help prevent cancer, STi's, obesity and heart problems. In order to keep healthy you should have a balanced diet, take exercise regularly and keep away from drugs such as caffine, nicotine, alcohol and illegal drugs such as solvents, depressents and stimulants.
Be aware that drugs are different from medicines in that drugs effect the brain whereas medicines do not. Medicines however need to be tested before treating humans therefore animal testing is often used, which gives rise to ethical issues.

Cells

Now, you should be aware of the labels associated with animal and plant cells, if not click on the link below. Understanding what role each part plays is also needed!
There are links to explain how substances move into and out of the cell, through the selectively permeable membrane. These processes are called diffusion, osmosis and active transport.
Also the cells you have learned to label are generalised cells, most cells are specialised so have a particular function. Keywords you must learn are differentiated cells, which are specialised, and undifferentiated cells, with no particular function known as stem cells.

Remember Mitosis?

Here you will look at how plants and animals differ in the way which they grow. Mitosis is the cell division which brings about growth and repair, plants are limited to the location of mitosis (meristems), however their cells retain the ability to differentiate if needed, which is how they can grow roots from their stems when we take cuttings. Animals however can perform mitosis in every cell which has a nucleus, yet if they are specialised, so differentiated, they can not change their function.
Growth is limited in plants by the ability to get water from it's roots to the tips of it's branches, where animals are limited to how well they can support themselves and how efficient their circulatory system is.

Enzymes - Biological Catalysts

Enzymes are made of proteins and speed up reactions within the body. Their names end in 'ase' and usually contain part of the name of the substrate (molecule) they are breaking down. E.g. carbohydrase, protease, lipase and urease. Other examples you should know are catalase, which breaksdown Hydrogen Peroxide and amylase, a carbohydrase specifically used on starch. Enzymes are specific to a particular molecule due to their active site. This shape is unique to the enzyme and substrate and is often described as being like a lock and key. If the enzyme is placed in an inhospitable environment, too hot or of an extreme pH, then the active site will denature, change shape, and the enzymes rate of reaction will slow and eventually not work at all.

Respiration

This is how the body releases energy from the glucose you eat. Performed in the mitochondria of cells, respiration can be with (aerobic) or without (anaerobic) oxygen. Aerobic respiration releases the most energy as is fully breaksdown glucose, using oxygen, to give carbon dioxide and water. Anaerobic respiration however is the incomplete breakdown of glucose to form lactic acid. This is due to the absence of oxygen and results in an oxygen debt being built up, which needs to be repaid if you are to breakdown the toxic lactic acid fully, to form carbon dioxide and water. As a consiquence anaerobic respiration releases less energy than aerobic respiration. It is important to note that respiration is NOT breathing. They are linked in that breathing takes in air, containing the oxygen needed for respiration and releases the carbon dioxide and water vapour produced (as by-products of respiration).

Digestion

You need to be able to name and understand the components of a balanced diet, name their enzyme (If they have one) and any nutrients produced by this breakdown. The name of the game is to make large insoluble molecules into small soluble molecules, so they can pass (be absorbed) through the small intestine into the blood. Carbohydrates, Proteins and Fats (Lipids) are too large to be absorbed so their corresponding enzymes break them down into Simple sugars, Amino acids and Fatty acids and glycerol respectively. Vitamins and Minerals are already small and soluble so they are rapidly absorbed into the blood, (So is alcohol and the glucose from sweets). Fibre however is not brokendown and therefore passes through the alimentary canal unchanged, so helps prevent us from being constipated. Lastly Water, essential for all biochemical reactions passes into the blood by osmosis.

Interdependence of Organisms

Food chains and more realistically food webs show how energy, originally from the sun (source) can be passed from plants (Photosynthesis) to animals (feeding) and from animals to other animals. This flow of ENERGY is represented by an ARROW and the use of vocabulary to describe the different organisms is critical in recognising the relationships between these organisms.

The Circle of Life! Two cycles need to be understood, Carbon and Nitrogen to fully appreciate how much influence every organism can have on each other.

The Circulatory System

All larger, multicellular organisms need a circulatory system, to supply all the cells of the body with oxygen and glucose for respiration and remove the carbon dioxide produces before it becomes toxic. Consisting of a heart to pump the blood around the body through blood vessels. Blood vessels involved are arteries, capillaries and veins. Arteries take blood Away from the heart, veINs take blood back INto the heart while capillaeries connect the two and are so thin they allow gaseous exchange between cells and the blood.

The Kidneys

As part of the urinary system, the kidneys clean the blood and help maintain homeostasis of water salts and glucose. The kidneys are connected to the bladder, where urine is stored, by ureters and urine is released from the body throught the urethra. The kidneys are made up of an outer cortex, medulla and pelvis. One million nephrons per kidney are positioned in the cortex and medulla and direct excess salts and water into the pelvis which leads to the ureter.
Nephrons begin with the Bowman's capsule, where ultrafiltration is used (high pressure filtering of the blood through a capillary knot into the nephron) this rids the blood of all the salt, water, glucose and urea, then selective reabsorption from the loop of Henle controls how much water, glucose and salt goes back into the blood. Excess water, salt and most of the urea is sent down the collecting duct to the pelvis of the kidney and is now called urine.

Microbes

Microorganisms are living organisms that are individually too small to see with the naked eye. The unit of measurement used for microorganisms is the micrometer (μ m); 1 μ m = 0.001 millimeter. Which means you need a microscope to see them.Microbes include Bacteria, Viruses and fungi.Fungi are the largest where bacteria are smaller and viruses are smaller again, however if there are enough of them you don't need a microscope then.
Microorganisms are found everywhere and are essential to many of our planets life processes. With regards to the food industry, they can cause spoilage, prevent spoilage through fermentation, or can be the cause of human illness. We can use bacteria in food preparation eg yoghurt, cheese production, also they are essential for life on the planet eg used in the Carbon and Nitrogen cycles. Fungi are also used to benifit humans eg bread and alcohol production also as decomposers, where penicillium is used to make the anti-biotic penicillin.Viruses however have NO use to us and only cause disease, a disease causing organism is refered to as a pathogen.

Enzymes

Enzymes are Biological Catalysts which work at an optimum rate in certain environments, they can be denatured at high temperatures and are highly specific to the substrate they breakdown (or build up), all of which you studied in B2. Enzymes are useful in industry as they require less energy for a reaction to occur and therefore save companies money, and often result in a higher yeild which makes companies more money. Examples are pectinase in fruit juice producion, protease in baby food manufacturing and washing powders.