Download Full Biology Science Notes and more Study notes Biology in PDF only on Docsity!
BIOLOGY
BIOENERGETICS
PHOTOSYNTHESIS:
During Photosynthesis sunlight (energy from the sun) is absorbed by green plants. The energy is used to convert carbon dioxide, water, and minerals the plants take in from the surroundings into sugar and gaseous oxygen. Photosynthesis is an endothermic reaction- takes in energy from surroundings.
FORMULA:
(Photosynthesis occurs in the leaf.)
NEEDS:
★ Chlorophyll (not used up). ★ CO2 (from air). ★ Water (from soil). ★ Sunlight energy (any light except green light)- not used up.
LIMITING FACTORS- a factor that slows down rate of photosynthesis. Main limiting factors: temperature, light intensity, carbon dioxide concentration.
Limiting factors may interact, and it may be any of them that is limiting photosynthesis. Example:
MEASURING + CALCULATING PHOTOSYNTHESIS:
In order to measure the rate of photosynthesis, we look at the amount of oxygen that a plant can produce, whilst changing one factor, e.g. light intensity.
With this experiment, you can investigate whether more oxygen bubbles are produced when more light bulbs are added. You would have to count the number of bubbles per minute.
INVERSE SQUARE LAW: Rate of photosynthesis is directly proportional to light intensity and inversely proportional to the distance from a light source. Inverse Square Law tells us Light Intensity is inversely proportional to the square of the distance from the source.
USING GLUCOSE:
The glucose produced in photosynthesis can be used for:
★ Respiration. ★ Converted into insoluble starch for storage. ★ Produce fat or oil for storage. ★ Produce cellulose, strengthens the cell wall. ★ Produce amino acids for protein synthesis.
PRODUCER- a living organism that can make their own food from the raw materials around them by a process called photosynthesis.
METABOLISM:
The chemical processes that occur in a living organism in order to maintain life. Metabolism includes- ★ Conversion of glucose to starch, glycogen and cellulose ★ The formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids ★ The use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins ★ Respiration ★ Breakdown of excess proteins to form urea for excretion.
CELL BIOLOGY
CELL DIVISION:
CHROMOSOMES:
The nucleus of a cell contains chromosomes made of DNA molecules. Each chromosome carries a large number of genes. In body cells, the chromosomes are usually found in pairs (23 pairs).
IMPORTANCE OF MITOSIS: Mitosis is needed for repair and replacement of cells: ★ at site of wound or injury ★ during growth spurts ★ during production of red blood cells in bone marrow (which happens all the time).
Mitosis takes place rapidly when an egg is newly fertilised, as the egg grows it develops further.
STAGES OF MITOSIS:
During mitosis, cells divide to produce two new ones which are exact copies of the original cell. Two daughter cells are produced from the parent cell. Each daughter cell has 46 chromosomes. All body cells divide by the process of mitosis, and are therefore identical to their parent cell. The only cells in the human body that do not undergo mitosis are the gametes, or sex cells (egg and sperm) which undergo a different process called meiosis. Egg and sperm cells each only have 23 chromosomes.
- During the cell cycle the genetic material is doubled and then divided into two identical cells.
- Before a cell can divide it needs to grow and increase the number of subcellular structures such as ribosomes and mitochondria. The DNA replicates to form two copies of each chromosome.
- In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides.
- Finally the cytoplasm and cell membranes divide to form two identical cells.
MICROSCOPES AND BACTERIA:
CELL DIFFERENTIATION:
As an organism develops, cells differentiate to form different types of cells.
★ Most types of animal cells differentiate at an early stage. ★ Many types of plant cells retain the ability to differentiate throughout life. ★ In mature animals, cell division is mainly restricted to repair and replacement.
As a cell differentiates, it acquires different subcellular structures to enable it to carry out a certain function- it has become a specialised cell.
SCALE AND SIZE- a scale bar may be used to find the magnification of the image.
Magnification = measured length / the number written
All measurements must be the same units, e.g. micrometres to nanometers- x1000.
MICROSCOPES:
Magnification of image formula:
BINARY FISSION:
Bacteria multiply by simple cell division (binary fission) as often as once every 20 minutes if they have enough nutrients and a suitable temperature. Bacteria can be grown in a nutrient broth solution (allows a liquid or gel to provide nutrients that a bacteria needs in order to grow) or as colonies on an agar gel plate. Uncontaminated cultures (otherwise other contaminating bacteria will try to compete for nutrients) of microorganisms are required for investigating the action of disinfectants and antibiotics.
ASEPTIC TECHNIQUES: Aseptic techniques must be used when culturing microorganisms in the laboratory so that there isn’t any bacteria that is trying to compete for nutrients in the petri dish. Harmful pathogens can also damage the results that are being collected. An autoclave must be used to prepare sterile growth medium and petri dishes. Sterile inoculating loops must be used to transfer microorganisms. The inoculating loop is sterilised when it is heated to red hot under a bunsen burner flame before and after use. Petri dishes and culture vials must also be covered.
COLONIES:
This can be used so that you can see how effective a specific antibiotic or antiseptic is. The cross-sectional
area of a colony or the clear area around it can be calculated using the following formula:
A=πr
NERVE CELL:
SPECIALISED CELLS:
There are many different types of cells in animals, and each type is specialised for a particular role. Organisms require different types of specialised cells that work together in order to function as a whole. Each specialised cell is adapted to its function.
XYLEM AND PHLOEM:
OSMOSIS ACTIVE TRANSPORT:
Osmosis is a specific type of diffusion. It is the movement of water from a high to low concentration through a partially permeable membrane. E.g. Plants absorb water from the soil by osmosis. Root hair cells are adapted for this by having a large surface area to speed up osmosis.
If a plant does not have enough water, it will be flaccid - this will mean that there is low pressure inside of the cell. If a plant has too much water, it will be turgid - this will mean that there is a high pressure inside of the cell.
ACTIVE TRANSPORT:
Active transport is the opposite of diffusion and osmosis as particles move from a region of low concentration to a region of high concentration. E.g. In the small intestine, epithelial cells in the villi will absorb glucose / Plant root hair cells absorb ions from the soil water.
Key: ● Purple oval: carrier protein ● ATP: energy required to move the particles from a low to high concentration ● Green squares: substances that are moving from a region of low to high concentration
ECOLOGY
FIELD WORK TECHNIQUES- a range of these can be used to determine the number of organisms in a given area. LIGHT METER- measures light intensity. QUADRAT- used to count the number of plants in a square metre. TRANSECT- used to record data at regular intervals. (Shown Below.)
MATERIAL CYCLE:
Different materials cycle through the abiotic and biotic components of an ecosystem. Physical abiotic factors such as temperature, light and humidity may change, but it is the chemical abiotic factors such as water, carbon, nitrogen, sulphur and oxygen that can be recycled. They will recycle by being transferred from one factor to another. All materials in the living world are recycled to provide the building blocks for future organisms. Biotic factors are the living things within an ecosystem, therefore it cannot be recycled. They tend to reproduce then die as a whole.
CARBON CYCLE:
★ When plants and animals decompose, carbon compounds are released into the soil. They are broken down by bacteria, which then releases the carbon back into the atmosphere. ★ Carbon returns into plants through photosynthesis. ★ When plants decay or are burned, they release carbon into the atmosphere in the form of carbon dioxide. ★ When plants are eaten, the carbon is transferred from the plant to the animal.
WATER CYCLE:
★ Also known as the hydrologic cycle ★ Sun provides the energy for water cycle to take place ★ Water is found in the atmosphere as water vapour through the process of evaporation, transpiration and sublimation. ★ Water returns to the earth through precipitation as rain, snow, sleet or hail. ★ Water seeps into the ground, and the plants and animals will take up some water. The rest of the water returns to the river and streams, then back into the ocean. ★ Some of the water will soak into the soil and rocks as groundwater. Some will be soaked deep in the soil, filling up the underground aquifers. ★ Providing drinking water through precipitation. However the water needs to be distilled through the process of thermal distillation. This removes the salt content in the precipitation, so that pure water is created.
COMPOSTING:
Rate of decomposition in composting can be affected by- temperature, water content, oxygen availability. ★ Colder temperatures will affect decomposing organisms so that they are less active ★ At extremely high temperatures, decomposers will be killed, therefore decomposition will stop ★ Low levels of water will mean that the decomposers cannot survive ★ High levels of water will increase the rate of decomposition, as decomposers tend to secrete enzymes onto decaying matter, then it absorbs any dissolved molecules. ★ High levels of oxygen will encourage decomposers to survive as they require oxygen to respire and survive.
DECAY:
This shows how quickly something is able to decay. We can use this formula to calculate the decay of specific substances (e.g. milk). We can see the change in pH value of milk when it is spoilt, as spoilt milk becomes acidic. Gardeners and farmers try to provide optimum conditions for rapid decay of waste biological material. The compost produced is used as a natural fertiliser for growing garden plants or crops. Anaerobic decay produces methane gas. Biogas generators can be used to produce methane gas as a fuel.
TROPHIC LEVELS:
● Level 1: Plants and algae make their own food and are called producers. ● Level 2: Herbivores eat plants/algae and are called primary consumers. ● Level 3: Carnivores that eat herbivores are called secondary consumers. ● Level 4: Carnivores that eat other carnivores are called tertiary consumers. Apex predators are
carnivores with no predators.
BIOMASS:
Pyramids of biomass represent the mass of the organism from each trophic level. E.g. Trophic level 1 at the bottom of the pyramid.
TRANSFER OF BIOMASS:
Biomass is lost between the different trophic levels. Producers are mostly plants and algae which transfer about 1 % of the incident energy from light for photosynthesis. Only approximately 10 % of the biomass from each trophic level is transferred to the level above it. This is why the pyramid of biomass gets smaller, as there are less organisms as we go higher up the trophic levels.
Losses of Biomass- Reasons: ★ Not all the ingested material is absorbed, some is egested as faeces ★ Some absorbed material is lost as waste, such as carbon dioxide and water in respiration and water and urea in urine ★ Large amounts of glucose are used in respiration
CALCULATING EFFICIENCY: The percentage efficiency of energy transfer between trophic levels can be calculated using the following equation: energy transferred to next level ÷ total energy in × 100
ECOSYSTEM:
ECOLOGICAL ORGANISATION:
There are 4 levels of ecological organisation. It starts at the lowest level: individual organisms, then populations, then communities, then finally to the whole ecosystem. Individual species of living organisms include every single plant and animal species that can be found on our planet. It also includes bacteria and fungi. Population- when you have a specific group of species that can live together in a specific area. Community- where each species depends on other species for food, shelter, pollination, seed dispersal etc. Ecosystem- is the biological environment that includes all living and nonliving things (e.g. air, soil and water) in a specific region, and the interactions that take place between them.
Communities may be affected by Abiotic or/ and Biotic factors.
ABIOTIC FACTORS- (Non-living physical factors that can affect living organisms in the community):
★ If there is a low temperature, there will be less photosynthesis. Low temperature would limit
the growth in plants. This is why there are normally less species living in colder climates.
★ If there is a low light intensity, there will be less photosynthesis. This will create less food for
the animals that would feed on the plants to survive. Some plants may become adapted by
having bigger leaves or a waxy layer so that it can optimise the process of photosynthesis.
★ If there is a low level of water, plants and animals would not survive as water is vital for
survival.
★ If there is a high level of pollution, animals would suffer as it affects their breathing system.
★ Soil pH and mineral content can also affect the plant growth.
★ Wind intensity and direction can also affect the plant growth.
★ Carbon dioxide levels can also affect the rate of photosynthesis in plants.
★ High oxygen levels are beneficial for aquatic animals.
CHANGES IN THE ENVIRONMENT:
ENVIRONMENTAL CHANGE:
Environmental changes affect the distribution of species in an ecosystem. These changes include:
★ Temperature - species will only be able to cope within a certain temperature range
★ Availability of Water - plants and animals must have sufficient levels of water in order to
survive
★ Composition of Atmospheric Gases - plants and animals require specific gases in order to
function
★ Seasonal - some species may not survive during specific seasons due to the change in the
temperature and the food available
★ Human Interaction - certain species are hunted by humans
BIODIVERSITY:
Biodiversity is the variety of all the different species of organisms on earth, or within an ecosystem. A great biodiversity ensures the stability of ecosystems by reducing the dependence of one species on another for food, shelter and the maintenance of the physical environment.
WASTE MANAGEMENT: Rapid growth in the human population and an increase in the standard of living means that increasingly more resources are used and more waste is produced. Unless waste and chemical materials are properly handled, more pollution will be caused.
Pollution can occur:
★ In water, from sewage, fertiliser or toxic chemicals.
★ In air, from smoke and acidic gases.
★ On land, from land ll and from toxic chemicals.
Pollution kills plants and animals, which reduces biodiversity.
LAND USE: Humans reduce the amount of land available for other animals and plants by building, quarrying, farming and dumping waste.
DEFORESTATION- when forests are taken down so that the land is used for something else (other than growing trees). Large-scale deforestation in tropical areas has occurred to:
★ Provide land for cattle and rice fields ★ Grow crops for biofuels ★ However, this reduces biodiversity as lots of plants and animals survive in the forests as they become extinct. It also removes the potential of medication to be obtained, as lots of medicines are found in a range of plants. It also ruins the habitats in which animals would normally survive. It also deeply affects the soil in the area. Deforestation also leads to an increase in carbon dioxide levels, which then leads to global warming.
GLOBAL WARMING:
Human activity is speeding up the rate of global warming. As humans burn more fossil fuels, more carbon dioxide is released into the atmosphere. Gases such as carbon dioxide form a layer around the Earth’s atmosphere. This layer normally allows heat from the sun to enter, and it stays within the atmosphere.
MAINTAINING BIODIVERSITY:
The way that humans interact within the ecosystem can have both a positive and negative impact on biodiversity. Biodiversity is when there is a variety of living organisms living in a specific habitat.
POSITIVE IMPACT NEGATIVE IMPACT
★ Conservation - trying to keep hold of all the natural resources that we have on the planet before it becomes extinct. ★ Use of fertilisers to grow more products for human consumption ★ Introduce non-indigenous species to kill off pests, so that more products can be produced without being ruined. ★ breeding programmes for endangered species ★ protection and regeneration of rare habitats ★ reintroduction of field margins and hedgerows in agricultural areas where farmers grow only one type of crop ★ reduction of deforestation and carbon dioxide emissions by some governments ★ Encouraging the recycling of resources rather than dumping waste in land falls.
★ Overuse of fertilisers - fertilisers include nitrates, and it may run from fields into the river when it rains. This causes algae to grow, and it blocks out light from the plants that want to photosynthesize. Bacteria will now break down the plants and use up the oxygen which animals will need in the water. ★ Fish farming - farming fish in a large area within the lake or sea is an issue as farmers will empty chemicals, waste, pathogens, and parasites into surrounding water. This reduces biodiversity as it harms other animals living nearby. Some fish will be fed on other wild fish, and the population of the wild fish will decrease. Some fish may escape and compete with the original fish that are found in the area. They will end up competing for the same food and habitat, therefore there will be less biodiversity. Some other fish may get trapped in the nets, and will die as a result of that. ★ New indigenous species that are introduced to kill pests may out-compete the natural species.
