What is Life?
This is no philosophical question. Well... maybe it is but, as far as biologists are concerned, life is whether something carries out all seven life processes. So... what are they?
Movement |
Travel from one area to another |
Animals move Plants 'move' towards light as they grow |
Respiration |
Release of energy from 'food' |
Often confused with breathing, you always respire unless you're dead. You can respire aerobically (with oxygen) or anaerobically (without) |
Sensitivity |
Detecting and responding to a stimulus (changes in the environment) pl: stimuli |
Examples are awareness, sight, growing towards light/water etc. |
Growth |
Increase of size or mass (amount of matter/particles that make us up) |
All life grows, usually via cell division |
Reproduction |
The production of offspring |
This can be sexual or asexual (which is alike to cloning) |
Excretion* |
Release of metabolic (cellular) waste |
Reactions, such as respiration, happen in cells and produce waste to be released such as gasses in gas exchange, urea and sweat |
Nutrition |
Use or production of nutrients |
Examples include: photosynthesis, ingestion, digestion etc. |
We like to remember these with the mnemonic: MRS GREN
*Excretion is often confused with egestion. Egestion is the removal of digestive waste and not metabolic waste. An example is faeces.
Homeostasis
Sometimes considered the eighth life process, this is the maintaining and controlling of the organism. For example, controlling cell turgidity, body temperature, water/glucose in the blood.
*Excretion is often confused with egestion. Egestion is the removal of digestive waste and not metabolic waste. An example is faeces.
Homeostasis
Sometimes considered the eighth life process, this is the maintaining and controlling of the organism. For example, controlling cell turgidity, body temperature, water/glucose in the blood.
Cells - Cell-iloquoy
Cells are the microscopic building blocks of life. (and atoms are the building blocks of cells...)
Every living thing (organism) is a cell (unicellular) or made of many cells (multicellular) In this section, we're only going to be talking about the cells of multicellullar organisms: animals and plants.
Every living thing (organism) is a cell (unicellular) or made of many cells (multicellular) In this section, we're only going to be talking about the cells of multicellullar organisms: animals and plants.
Human cells start off as unspecialised stem cells which differentiate to form the various cells of your body which are each specialised for their purpose. These cells vary from blood cells to sex cells (gametes) to skin cells and wouldn't be what they were if it weren't for specialisation.
Molecules and Enzymes - Chemistry???
Diffusion, Osmosis and Active Transport
concentration - the amount of particles (of a type) in an area
Organisms are made of organs which are made of tissues (groups of cells) which are made of cells which are made of organelles. Those are made of molecules and atoms: 'the building blocks of the universe' which follow some rules...
concentration - the amount of particles (of a type) in an area
Organisms are made of organs which are made of tissues (groups of cells) which are made of cells which are made of organelles. Those are made of molecules and atoms: 'the building blocks of the universe' which follow some rules...
- Diffusion is the movement of particles from an area of high concentration to an area of low concentration.
- Osmosis is the movement of water molecules from an area of high water concentration to an area of low water concentration across a partially-permeable membrane (something which only allows some things [eg: water] through it).
- Active Transport is the movement of particles from an area of high concentration to an area of low concentration. (Against the concentration gradient), which requires energy.
Enzymes
Enzymes are 'biological catalysts' which break down or synthesise molecules called substrates when they contact the enzyme's active site. This is the area of the enzyme that the substrate(s) binds to for the reaction to take place. Each enzyme has a specifically shaped active site for specific substrates which are the only ones which fit. This is called the lock and key model and the enzyme and substrate(s) are called complementary. When the substrate(s) binds with the enzyme temporarily, it is called an enzyme-substrate complex.
Enzymes work using collision theory which states that particles need to hit each other and in the right way for a chemical reaction to take place. As a result, the hotter the temperature, the more the particles move so the more likely they are to have successful collisions. This means the enzymes work better in higher temperatures. But if the temperatures get too high, enzymes denature (stop working due to deformation of the active site). When an enzyme is too far from it's correct pH (acidity of environment) it also denatures.
When the temperature or pH is at it's best for enzyme efficiency, it is called: optimum temperature/pH
Enzymes are 'biological catalysts' which break down or synthesise molecules called substrates when they contact the enzyme's active site. This is the area of the enzyme that the substrate(s) binds to for the reaction to take place. Each enzyme has a specifically shaped active site for specific substrates which are the only ones which fit. This is called the lock and key model and the enzyme and substrate(s) are called complementary. When the substrate(s) binds with the enzyme temporarily, it is called an enzyme-substrate complex.
Enzymes work using collision theory which states that particles need to hit each other and in the right way for a chemical reaction to take place. As a result, the hotter the temperature, the more the particles move so the more likely they are to have successful collisions. This means the enzymes work better in higher temperatures. But if the temperatures get too high, enzymes denature (stop working due to deformation of the active site). When an enzyme is too far from it's correct pH (acidity of environment) it also denatures.
When the temperature or pH is at it's best for enzyme efficiency, it is called: optimum temperature/pH
Organisms and Microorganisms - an organic summary
All organisms can be split (classified) into 5 kingdoms...
Cells: Animals are multicellular organisms without cell walls and are eukaryotic (their cells have nuclei).
Food: Animals are heterotrophic (feed on others) and eat other animals or plants
Carbohydrate Store: Animals store carbohydrates as fat (glycogen and polysaccharides)
Examples: Humans, Wolves, Mosquitos, snakes, falcons
Food: Animals are heterotrophic (feed on others) and eat other animals or plants
Carbohydrate Store: Animals store carbohydrates as fat (glycogen and polysaccharides)
Examples: Humans, Wolves, Mosquitos, snakes, falcons
Cells: Plants are multicellular organisms with cell walls of cellulose and are eukaryotic (their cells have nuclei).
Food: Plants are autotrophic (self feeding) and produce food via photosynthesis. (making them phototrophic)
Carbohydrate Store: Plants store carbohydrates as starch (and sucrose)
Examples: Pea plants, Maise plants, Trees, Cereal, Fern
Food: Plants are autotrophic (self feeding) and produce food via photosynthesis. (making them phototrophic)
Carbohydrate Store: Plants store carbohydrates as starch (and sucrose)
Examples: Pea plants, Maise plants, Trees, Cereal, Fern
Cells: Fungi can be multicellular or unicellular organisms made of hype with cell walls of chitin and are eukaryotic (their cells have nuclei).
Food: Fungi are saprotrophic (feeds on dead organic matter) and feed by secreting extracellular digestive enzymes to break down the dead material into smaller soluble molecules that they then absorb.
Carbohydrate Store: Fungi store carbohydrates as glycogen (as seen in the above diagram)
Examples: Yeast (unicellular), Mucor (multicellular), Penicillium (multicellular), Mushrooms, Torula
Some multicellular fungi form thread-like structures called mycelium consistingof hyphae (sg: hypha) as shown below:
Food: Fungi are saprotrophic (feeds on dead organic matter) and feed by secreting extracellular digestive enzymes to break down the dead material into smaller soluble molecules that they then absorb.
Carbohydrate Store: Fungi store carbohydrates as glycogen (as seen in the above diagram)
Examples: Yeast (unicellular), Mucor (multicellular), Penicillium (multicellular), Mushrooms, Torula
Some multicellular fungi form thread-like structures called mycelium consistingof hyphae (sg: hypha) as shown below:
note: The hyphae are not divided into separate cells
Cells: Bacteria are unicellular organisms with cell walls of peptidoglycan and are prokaryotic (their cells don't have nuclei). Instead, their DNA is left loose in the cytoplasm or in rings called plasmids (not all bacteria have plasmid). They can also have flagella, cilia and/or a capsule.
Food: Bacteria can feed on living or dead organisms. Some also have a form of chlorophyll so can photosynthesise
Carbohydrate Store: Bacteria don't store carbohydrates
Examples: Lactobacillus (helpful), Pneumococcus (harmful), salmonella bacterium (harmful)
Food: Bacteria can feed on living or dead organisms. Some also have a form of chlorophyll so can photosynthesise
Carbohydrate Store: Bacteria don't store carbohydrates
Examples: Lactobacillus (helpful), Pneumococcus (harmful), salmonella bacterium (harmful)
This is effectively the kingdom for everything that doesn't fit into the other kingdoms.
Cells: Protoctista (protoctists) are unicellular organisms usually though can be multicellular with cell walls of protein (though not always) and are eukaryotic (their cells have nuclei).
Food: They can be autotrphic (feed themselves) and photosynthesise
Examples: Algae, Amoeba, Plasmodium, chlorella
They are often broken up into the more animal-like protozoa and the more plant-like algae.
Cells: Protoctista (protoctists) are unicellular organisms usually though can be multicellular with cell walls of protein (though not always) and are eukaryotic (their cells have nuclei).
Food: They can be autotrphic (feed themselves) and photosynthesise
Examples: Algae, Amoeba, Plasmodium, chlorella
They are often broken up into the more animal-like protozoa and the more plant-like algae.
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Viruses are not living organisms as they do not carry out any of the seven life processes*. They do not feed nor contain a nucleus - they have a nucleoid containing RNA/DNA instead. They are parasites which can only reproduce in cells by using its genetic material to reprogram the host cell (cell it takes over).
Examples: Influenza, HIV, TMV *viruses can reproduce though only in cells |
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Miroscopy and other skills
- Biologists regularly need mathematical ability, particularly when dealing with maths or simple calculations.
- The majority of the scientific skills you need for the sciences such as biology can be found on this page.
- Biologists often use microscopes to look at microscopic things such as the structure of tissues or individual cells so it is important to know how to use these. It is also useful to be able to calculate the actual size of something seen through a microscope and how much a microscope is magnifying an image by:
{Microscope Magnification} = {Size of Image} / {Real Size of Specimen}
Biologists are often also able to draw the images shown through the microscope. This doesn't require good art skills and it need only be a copy of what is seen in the microscope with horizontal (where possible) lines drawn from the diagram for labelling.
The image below from this source shows a light-microscope, labelled.
They eyepiece is what one looks through. The coarse and fine focus control the clarity of the image by moving the stage or objective lenses. The objective lenses have different magnifications that allow the specimen to be seen and the slide with the specimen on is places on the stage under the stage clips.
When looking at the specimen, it's typically logical to view the lower magnifications first. |
Preparing Slides
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Types of Microscopes There are light-microscopes and Electron-microscopes. Light microscopes tend to have lower resolutions than electron-microscopes and work using light from a bulb or reflected by a mirror. resolution- The ability to distinguish between 2 points (as opposed to seeing one). A 200nm resolution such as those of light-microscopes means it cannot distinguish between points closer than 200nm apart. Electron Microscopes use beams of electrons instead of light and come in 2 types. Transmission Electron Microscopes (TEMs) and Scanning Electron Microscopes (SEMs). They provide clearer images and better resolutions (<1nm and 50nm respectively). For these, samples are placed in a vacuum and so aren't living cells. |