BIOLOGY STUDY NOTES
PATTERNS IN NATURE
Cell theory
The work of Hooke (recorded the compartmentalised nature of cork and named them ‘cells’ more then 150 year before) and Brown (discovered the nucleus 6 years before). Without them Schlieden and Schwann could not have built their cell theory which is the valid theory today
Louis Pasteur – micro-organisms arose from pre-existing organisms
The construction and improvement of lens has enable a view of the cell’s internal structure and led to the development of the cell theory. The creation of the electron microscope enables even more detailed observations of cells, because it has a higher resolution and magnification unlike the light microscope.
Resolution- ability to deliver clear details of image
Magnification- how much the microscope enlarges the object being viewed
Inorganic – contain elements other than carbon combined with hydrogen, make up the non-living structures
Living organisms use organic and inorganic compounds to functions. Inorganic compounds contained in cells are water, oxygen and salts. Organic compound found in living organisms are carbohydrates, proteins, lipids, and nucleic acids.
The movement of these cells occurs across cell boundary- cell membrane which controls entry of water, and other molecules.
Cell membrane is selectively permeable allowing only certain molecules to pass though.
In 1972 Singer and Nicholson proposed selectively permeable membrane as a fluid-mosaic, a ‘lipid sea’ with ‘many various proteins floating in it’
Membranes are composed of 40% lipids and 60% proteins.
Lipid component:
Made of 2 layers of phospholipids:
These phospholipids are arranged in a bilayer
Protein Component:
Protein molecules are scattered throughout bilayer. They either:
Movement of molecules across cell membranes
The permeability of a membrane to a molecule depends on the molecules:
Water-soluble molecules are highly charged therefore do not penetrate easily. But they are highly permeable because of osmosis.
Molecules that have low permeability rely on carrier proteins to transport them across membranes in cells
Osmosis
Substance that moved- water
Concentration gradient- low to high
Energy requirement-none
Osmosis is the movement of water molecules across a semi-permeable membrane, from a low solute concentration to a high solute concentration (high water to low water). Requires no energy input.
The water moves through special tiny protein channels (pores) called aquaporins.
Diffusion
Substance that moved- any molecules
Concentration gradient- high to low
Energy requirement-none
Diffusion is the movement of any molecules from a high concentration to a low concentration until the concentration is the same.
In living cells, diffusion is a way at which the cells take in materials from the environment and also the way of ridding any unwanted material
Active transport
Substance that moved- molecules
Concentration gradient- low to high
Energy requirement-input of energy
Active transport is the movement of molecules from an area of low concentration to an area of high concentration, requiring the input of energy.
Volume- is the capacity inside the cell. Determines the metabolic needs and waste products.
Surface Area / Volume = SA: V
As a cell grows larger its rate of exchanging and removing of materials and wastes decreases, so if the cell grows too big it divides into two cells so it can maintain an efficient surface area to volume ratio as smaller cells are more efficient.
Unicellular- single celled, simple diffusion and some osmosis
Multicellular- many cells, diffusion and osmosis
Different types of cells have different structures and activities, but they work together so that the organism functions as a coordinated whole.
Self-feeding organisms. Can make organic materials to feed themselves through photosynthesis. E.g. carbon dioxide, water, inorganic material.
Feed on something different. Obtain the substances they need from their external environment, from autotrophs.
Photosynthesis requires:
Role in ecosystems:
Photosynthesis occurs in two stages:
During the day the sugar is stored as starch in the leaf and at night, they are converted back to sugars.
Mineral uptake- by diffusion
ROOT FUNCTIONS
TYPES OF ROOT SYSTEMS
ROOT HAIR LAYERS
MOVEMENT OF WATER & MINERALS ACROSS ROOTS
Water and minerals:
Structure of leaves in relation to their function
Leaves are very important as all life depends on their photosynthesis as a source of food, their energy.
The structural features needed by a leaf:
Leaves are broad, flat, thin ® large SA ® capture of sunlight, exchange of gases ® for photosynthesis
HETEROTROPHS OBTAINING NUTRIENTS
Ingestion:
The intake of food into a digestive tract (multicellular organisms) or into a cell (unicellular). Intake of complex organic food is eating
Digestion:
Breakdown of complex insoluble food into simpler, smaller, soluble molecules (such as amino acids- proteins, fatty acids and glycerol- lipids) that can be absorbed.
Absorption:
When basic units of food (glucose, amino acids, fatty acids, glycerol) are absorbed across digestive tract into bloodstream
Assimilation:
Conversion of absorbed simple substances into more complex useful molecules which become part of a structure of organism or used as energy
Egestion:
Elimination of undigested food as waste. E.g. fibre that cannot be digested.
The digestion of foods involves two stages:
ENZYMES
Most digestive enzymes split food molecules by hydrolysis, in which a molecule is split at a particular point by adding a water molecule. There are 3 types of enzymes:
Large food molecules are broken down several enzymes
There are four main types:
Carnivores: have large canines to tear and rip meat carcasses
Herbivores: have no canines, but have large flat double teeth to grind plant food
Omnivores: have some teeth for tearing and cutting meat and others for grinding plant food
Respiratory system
Excretory organs:
Characteristics of gas exchange systems include:
PATTERNS IN NATURE
- Organisms are made of cell that have similar structural characteristics
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Cell theory
- Cells are the basic units of life, making up all living things
- All cells come from pre-existing cells
- All living things are made up of one or more cells
- Cells are the basic structural and functional unit of organisms
- All energy flows of life occurs within cells
- Outline the historical development of cell theory, in particular the contribution of Robert Hooke and Robert Brown
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| 1590 | Han & Jansen | Made first compound microscope (placed two convex lenses in a tube) |
| 1663 | Robert Hooke | Introduced the term ‘cell’ while observing cork under a light microscope, worked at improving the microscope, telescope and barometer. |
| 1674-1682 | Anton Van Leeuwenhoek | Made lenses of higher quality. Discovered unicellular organisms. Also bacteria. |
| 17th | Henri Dutrochet | Suggested that cells are the basic units of life |
| 1801 | Robert Brown | First described the cell nucleus while observing plant cells in an orchid. Noticed the random movement of pollen grains (Brownian motion). |
| 1838 | Matthias Schleiden | Stated that parts of plants are made of cells (not visible to the unaided eye). |
| 1839 | Theodor Schwann | Stated that animals are made of cells (agreed with Schleiden). They |
| | Schleiden & Schwann | Published the cell theory in a book, stating that: 1. The cell is the unit of structure of all living things. 2. The cell exists as distinct entity & building block in construction of organisms. |
| 1855 | Rudolph Virchow | Introduced idea that cells reproduce by dividing, stating all living cells can only arise from other living cells |
| 1933 | Ernst Ruska | Built the fi rst electron microscope |
| 1938 | Fritz Zernike | Invented the phase contrast microscope-used to observe living, unstained cells |
| 1955 | Marvin Minsky | Invented the scanning electron microscope |
The work of Hooke (recorded the compartmentalised nature of cork and named them ‘cells’ more then 150 year before) and Brown (discovered the nucleus 6 years before). Without them Schlieden and Schwann could not have built their cell theory which is the valid theory today
- Describe evidence to support cell theory
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Spontaneous generation theory – organisms originated from inanimate (non-living) materials. - Theory was disapproved by:
Louis Pasteur – micro-organisms arose from pre-existing organisms
- Rudolf Virchow- proposed theory: all cells come from pre-existing cells. This disapproves spontaneous generation
- The improvements in the microscopes
- The electron microscope could view more detail in the cells
- Discovery of cell division
- Spontaneous generation: belief that creatures could originate from inanimate (non-living) material.
- Discuss the significance of technological advances to cell theory development
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| Light microscope | Electron microscope |
| Uses light to view | Uses electron beams to view |
| Low resolution | High resolution |
| Low magnification | High magnification |
| Can view living active organisms | Organism must be dead |
| Less expensive, small and easily maintained | Very large, expensive, and kept at constant temperature & pressure |
| Cannot see internal structures (only at cellular level) | Can see internal structures (sub-cellular level) as it shows huge detail |
The construction and improvement of lens has enable a view of the cell’s internal structure and led to the development of the cell theory. The creation of the electron microscope enables even more detailed observations of cells, because it has a higher resolution and magnification unlike the light microscope.
Resolution- ability to deliver clear details of image
Magnification- how much the microscope enlarges the object being viewed
- Identify cell organelles seen with light & electron microscope
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Organelles you can see through a: | Light microscope | Electron microscope | |
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- Describe relationship between structure of organelles and function
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| Organelle | Structure | Function | Plant / Animal cell |
| Mitochondria | | Site of aerobic respiration | Plant & Animal |
| Nucleus | | Controls cell activities. Contains cell’s DNA | Plant & Animal |
| Nucleolus | | Manufacture of proteins-ribosomes | Plant & Animal |
| Endoplasmic reticulum | | Connects cell membrane with nuclear membrane, transports materials | Plant & Animal |
| Ribosomes | | Produces protein from amino acids | Plant & Animal |
| Golgi body | | Packages and stores proteins in its vesicles, before secretion | Plant & Animal |
| Cell membranes | | Semi-permeable membrane, protects & supports organelles and made of double layer of phospholipids | Plant & Animal |
| Chloroplast | | Site of photosynthesis, contains the green colour | Plant |
| Lysosomes | | Dissolves large food molecules to small molecules, breaking down proteins, carbs, lipids | Animal |
| Cell wall | | Protects & supports the cell, maintains cell structure | Plant |
| Vacuole | | Stores food, water, dissolved solutes and waste. More in plants | Plant & Animal |
- Membranes around cells provide separation & links with external environment
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- Identify the major groups of substances found in living cells and their uses in cell activities
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Chemicals found in cells are grouped in to 2 different groups:Inorganic – contain elements other than carbon combined with hydrogen, make up the non-living structures
- Gases including: CO₂ (carbon dioxide) even though it contains carbon it does not have hydrogen with it, O₂ (oxygen)
- Mineral salts such as calcium salts, sodium chloride and phosphates
- H₂0 (water)
- Carbohydrates- sugars and starch
- Proteins
- Lipids- fats and oils
| Organic compounds | Composition | Function | Forms of organic compound |
| Carbohydrates | Carbon Hydrogen Oxygen | Used for respiration, when energy is needed the glucose is broken down | Monosaccharides- the basic building blocks of more complex carbohydrates Disaccharides, i.e. sucrose, lactose, maltose Polysaccharides i.e. starch is the main food store for plants. |
| Proteins | Carbon Hydrogen Oxygen Nitrogen | Used in the structure, storage, movement and transport of cells | Amino acids is the basic unit for protein, it joins together by peptide bonds to form polypeptides |
| Lipids | Carbon Hydrogen Oxygen | Stores energy but is more difficult to release than carbohydrates. It breaks down into fatty acids and glycerol | Fats, oils, waxes and steroids |
| Nucleic acids | Sugar, Nitrogen Phosphate | A vital role for heredity. Nucleic acids are long – chain of nucleotides | DNA, RNA, these are the most complex and largest organic compounds |
Living organisms use organic and inorganic compounds to functions. Inorganic compounds contained in cells are water, oxygen and salts. Organic compound found in living organisms are carbohydrates, proteins, lipids, and nucleic acids.
- Identify that there is movement of molecules into and out of cells
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For any cell to function substances need to enter and exit the cell through its cell membrane. Substances for functioning need to move in to cells (gases, nutrients and water). Waste substances (urea, uric acid, excess carbon dioxide), products secreted that are needed to coat outside of cell (mucus) and substances that need to be passed to other cells (hormones) need to move out of cells.The movement of these cells occurs across cell boundary- cell membrane which controls entry of water, and other molecules.
Cell membrane is selectively permeable allowing only certain molecules to pass though.
- Describe current model of membrane structure and explain how it accounts for movement of some substances into & out of cells
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Fluid mosaic model- current model of membrane structureIn 1972 Singer and Nicholson proposed selectively permeable membrane as a fluid-mosaic, a ‘lipid sea’ with ‘many various proteins floating in it’
Membranes are composed of 40% lipids and 60% proteins.
Made of 2 layers of phospholipids:
- Hydrophobic tails facing in
- Hydrophilic heads facing out
Protein Component:
Protein molecules are scattered throughout bilayer. They either:
- Cholesterol molecules- embedded within membrane
- Carbohydrates- attached to external surfaces
- Integral protein- span the length of bilayer forming channels
- Peripheral proteins- attached to integral proteins
- Glycoproteins- have attached carbohydrates for cell recognition
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Movement of molecules across cell membranes
The permeability of a membrane to a molecule depends on the molecules:
- Size:
- Electrical charge:
- Lipid solubility:
Water-soluble molecules are highly charged therefore do not penetrate easily. But they are highly permeable because of osmosis.
Molecules that have low permeability rely on carrier proteins to transport them across membranes in cells
- Compare the process of diffusion and osmosis
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| OSMOSIS | Substance that moved | Water molecules |
| Concentration gradient | Low to high | |
| Energy requirement | None | |
| Only across selectively permeable membranes | Yes | |
| Examples | Plant cells exposed to air lose water to surroundings by osmosis | |
| DIFFUSION | Substance that moved | Any molecules |
| Concentration gradient | High to low | |
| Energy requirement | None | |
| Only across selectively permeable membranes | No | |
| Examples | Human- oxygen from cells of lungs moving into blood capillaries | |
| ACTIVE TRANSPORT | Substance that moved | Molecules |
| Concentration gradient | Low to high | |
| Energy requirement | Input of energy | |
| Only across selectively permeable membranes | Yes | |
| Examples | White blood cell in human body engulfs & digests bacteria fighting infection |
Substance that moved- water
Concentration gradient- low to high
Energy requirement-none
Osmosis is the movement of water molecules across a semi-permeable membrane, from a low solute concentration to a high solute concentration (high water to low water). Requires no energy input.
The water moves through special tiny protein channels (pores) called aquaporins.
Diffusion
Substance that moved- any molecules
Concentration gradient- high to low
Energy requirement-none
Diffusion is the movement of any molecules from a high concentration to a low concentration until the concentration is the same.
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In living cells, diffusion is a way at which the cells take in materials from the environment and also the way of ridding any unwanted material
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Active transport
Substance that moved- molecules
Concentration gradient- low to high
Energy requirement-input of energy
Active transport is the movement of molecules from an area of low concentration to an area of high concentration, requiring the input of energy.
- Explain how surface area to volume ratio affects the rate of movement of substances into and out of cells
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Surface area- is the outside area of the cell. Controls the rate of removal and absorption of wastes and nutrients.Volume- is the capacity inside the cell. Determines the metabolic needs and waste products.
Surface Area / Volume = SA: V
As a cell grows larger its rate of exchanging and removing of materials and wastes decreases, so if the cell grows too big it divides into two cells so it can maintain an efficient surface area to volume ratio as smaller cells are more efficient.
- OBTAINING NURTIENTS
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Unicellular- single celled, simple diffusion and some osmosis
Multicellular- many cells, diffusion and osmosis
- Identify some examples that demonstrate the structural and functional relationships between cells, tissues, organs and organ systems in multicellular organisms.
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Different types of cells have different structures and activities, but they work together so that the organism functions as a coordinated whole.
| Sperm | Head section that contains nucleus enabling it to penetrate the egg at fertilisation. Mitochondria in the middle section provides energy, and a tail to propel itself |
| Red blood cell | Disc – shaped and lack of nucleus, contains red pigment haemoglobin which is responsible for oxygen transport |
| White blood cell | Colourless cell, contains a nucleus and helps fight infections |
| Plant epidermal cells | Layer that protects the cells (outermost layer) in a plant which allow gaseous exchange. |
| Tissues | Groups of cells that are similar in structure and function. For example, muscle cells make up tissues of a stomach. |
| Organs | Groups of similar tissues make up organs. For example, the tissues of a stomach make up a stomach, which is an organ. |
| Systems | Groups of similar organs make up a system within the body. For example, the organs like stomach make up the digestive system in humans. |
- Distinguish between autotrophs and heterotrophs in terms of nutrient requirements.
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Autotrophs Self-feeding organisms. Can make organic materials to feed themselves through photosynthesis. E.g. carbon dioxide, water, inorganic material.
- Plant cells
- Have chloroplasts
Feed on something different. Obtain the substances they need from their external environment, from autotrophs.
- Animal cells
- Do not have chloroplasts.
- Identify the materials required for photosynthesis and its role in ecosystems
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- Light (energy)
- chlorophyll
- carbon dioxide
- water
- to make: sugars and oxygen
Role in ecosystems:
- photosynthesis is the initial path of energy for all ecosystems
- organisms that photosynthesise are producers: which form the basis of all food webs providing glucose.
- Glucose can be converted & stored as : lipids, proteins, carbohydrates
- Organic compounds which rely on photosynthesis for their production
- Provide the structural basis for all living cells
- Source of energy for all cellular processes
- Identify the general word equation for photosynthesis and outline this as a summary of a chain of biochemical reactions
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Photosynthesis occurs in two stages:
- Light phase (photolysis)
- Light-independent phase (carbon-fixation stage)
During the day the sugar is stored as starch in the leaf and at night, they are converted back to sugars.
- Explain the relationship between the organisation of the structures used to obtain water and minerals in a range of plants and the need to increase the surface area available for absorption
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Water uptake- by osmosisMineral uptake- by diffusion
ROOT FUNCTIONS
- To absorb water and mineral from the soil
- To anchor the plants
- To act as a store of food in some plants
TYPES OF ROOT SYSTEMS
| Tap roots |
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| Fibrous roots |
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| Mycorrhiza |
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| Aerial roots |
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- Located behind root cap
- Increase surface area for water uptake
- Approx. 4mm long
- Have a slender and flexible slippery structure which allows them to penetrate between soil particles.
MOVEMENT OF WATER & MINERALS ACROSS ROOTS
Water and minerals:
- Enter through epidermal
- Move across root to xylem (water-conducting tissue in centre of root)
- Water moves by osmosis through the cells
- Water and minerals move across cortex into central vascular tissue
- Xylem transports water and dissolved mineral salts from the roots up to rest of plant
- Explain the relationship between the shape of leaves, the distribution of tissues in them and their role
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The role of leaves- Absorb sunlight
- Make food
- Transpiration- to release water to cool plant down and create a suction pull to lift water from roots to the top of plant.
- To absorb sunlight and carbon dioxide
- To release oxygen
- To provide chlorophyll
- Make glucose and transport to other parts of plants
Structure of leaves in relation to their function
The structural features needed by a leaf:
- Large surface area: to absorb light and carbon dioxide
- Pores in the leaf surface: exchange of gases with environment
- Cells inside that contain chloroplasts: trap energy of sunlight
- Water transport system: form roots to leaves
- Food transport system: from leaves to other parts of plant
Leaves are broad, flat, thin ® large SA ® capture of sunlight, exchange of gases ® for photosynthesis
| TISSUE | CELL TYPE | POSITION IN LEAF | FUNCTION | STRUCTURAL SUITABILITY |
| Epidermis | Epidermal cells | Top and lower surface just below the cuticle | Protect delicate inner tissues and prevent evaporation by secreting a waterproof cuticle | Simple, flattened cells |
| Guard cells | In the epidermis and surrounding the stomata pore | Control the exchange of gasses and loss of water | Bean-shaped cells occurring in pairs: protecting from both sides (two of them) for efficiency | |
| Mesophyll | Palisade cells | DORSIVENTRAL LEAF Right below upper epidermis | Main photosynthetic cells in leaves | Elongate cells containing numerous chloroplasts for its function of photosynthesis |
| ISOBILATERAL LEAF Above the lower and below the upper epidermis | ||||
| Spongy cells | Beneath the palisade tissue and above the lower epidermis | Main role is Gaseous exchange and second most important for photosynthesis | Irregular in shape and have fewer chloroplasts. They have large air spaces for gaseous exchange |
HETEROTROPHS OBTAINING NUTRIENTS
- Describe the role of teeth in increasing the surface area of complex foods for exposure to digestive chemicals
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SOME DEFINITIONSIngestion:
The intake of food into a digestive tract (multicellular organisms) or into a cell (unicellular). Intake of complex organic food is eating
Digestion:
Breakdown of complex insoluble food into simpler, smaller, soluble molecules (such as amino acids- proteins, fatty acids and glycerol- lipids) that can be absorbed.
Absorption:
When basic units of food (glucose, amino acids, fatty acids, glycerol) are absorbed across digestive tract into bloodstream
Assimilation:
Conversion of absorbed simple substances into more complex useful molecules which become part of a structure of organism or used as energy
Egestion:
Elimination of undigested food as waste. E.g. fibre that cannot be digested.
The digestion of foods involves two stages:
- Mechanical breakdown- food is chewed and large chunks are physically broken down into smaller bits
- Chemical breakdown- digestive enzymes act on the food to chemically break down the large complex molecules into smaller, simpler molecules.
ENZYMES
Most digestive enzymes split food molecules by hydrolysis, in which a molecule is split at a particular point by adding a water molecule. There are 3 types of enzymes:
- Amylases - act on carbohydrates.
- Proteases - act on proteins
- Lipases - act on lipids.
Large food molecules are broken down several enzymes
- Teeth mechanically break the complex food into smaller pieces increasing the SA for exposure to digestive chemicals i.e. enzymes.
- Saliva then lubricates the food for easier swallowing
- The amylase digests starch to maltose
There are four main types:
| 1. | INCISORS | Front teeth | Grasp hold and bite food |
| 2. | CANINES | Eye teeth/fangs | Stabbing, gripping prey and tearing flesh |
| 3. | PREMOLARS | Cheek teeth | Chewing, cutting flesh, cracking bones |
| 4. | MOLARS | Back teeth | Grinding, crushing, chewing food |
Carnivores: have large canines to tear and rip meat carcasses
Herbivores: have no canines, but have large flat double teeth to grind plant food
Omnivores: have some teeth for tearing and cutting meat and others for grinding plant food
- Proteins are absorbed after being broken down to amino acids.
- Carbohydrates are absorbed after being broken down to simple sugars (monosaccharides).
- Lipids are absorbed after being broken down to fatty acids and glycerol.
- Vitamins, minerals and water are absorbed directly.
- Explain the relationship between the length and overall complexity of digestive systems of a vertebrate herbivore and a vertebrate carnivore with respect to:
- the chemical composition of their diet
- the functions of the structures involved
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| Type of animal | Chemical composition of diet | Functions of the structure involved |
| Herbivore | Herbivores have much longer intestines because cellulose is much harder to digest, their diet mainly composed of cellulose and food may remain there for a long time. No vertebrate can produce a fluid that can digest cellulose, so instead the micro – organisms convert cellulose to sugars. | Herbivores have 4 chambers, in the first chamber, rumen, where the food is acted upon by bacteria. It then moves to the honey comb bag where the food is chewed again. After chewing, the food goes to the third stomach where it is strained and is passed to the last chamber, the true chamber, where the gastric juices are secreted. |
| Carnivore | Carnivores have simple stomachs, they eat meat which requires less digestion | The acid in the stomach breaks down some muscle tissue and the protease digestive enzyme. The fats are broken down by the lipase enzymes. Protein and fat contain a higher amount of energy per gram than plant material, so they can eat less to gain the same amount of energy. |
- Gaseous exchange and transport systems transfer chemicals through the internal and between the external environments of plants and animals
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Gaseous exchange is the movement of gases by diffusion across cell membranes. Gases move into cells and others are expelled- Compare the roles of respiratory, circulatory and excretory systems
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| Systems | Roles |
| Respiratory | Allows gas exchange for an organism |
| Circulatory | System to circulate materials to supply cells with nutrients and remove wastes |
| Excretory | Allows the excretion of waste products |
Respiratory system
- Take in oxygen
- As it is needed for release of energy from food
- Remove carbon dioxide
- Is a waste that must be moved because it is toxic in large quantities
- Allows gaseous exchange between organism and its external environment
- Respiratory system made of tissues and organs for gaseous exchange
- Transport of gases, nutrients waste products, hormones, antibodies
- Maintains a constant internal environment (stabilizes pH levels)
- Removes toxins and pathogens
- Stabilizes body temperature
- Remove metabolic wastes from transport medium
- Expel these nitrogenous wastes
Excretory organs:
- Identify and compare the gaseous exchange surfaces in an insect, a fish, a frog and a mammal
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| INSECT |
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| FISH | Respiratory organs are internal gills
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| FROG | Gas exchange surfaces: Skin- main site for respiration when in water. Well supplied with blood vessels Floor of mouth- serves as buccal pump ventilating lungs. Well supplied with blood capillaries Lungs- pair of simple sacs used only when frog is active. Nostrils have valves that close to prevent the entry of water into the lungs All three surfaces are thin, moist and well supplied with blood |
| MAMMAL | Gaseous exchange takes place in millions of alveoli (air sacs) in the lungs
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- A large surface area
- Moist, thin surface
- Near to an efficient transport system
| Organism | Gaseous exchange surfaces |
| Insects | Tracheae, a system of branching tubes. The tracheae opens through the spiracles along the abdomen, it branches throughout the tissues of the insects bringing air directly to the cells. |
| Fish | Gills over which water flows. Gills provide an external gas exchange surface. The gill filaments spread out to increase surface area, the rich supply of blood vessels enable gases to and from the gills. |
| Frogs | Lung and the skin, oxygen from the air diffuses into the moist skin which is transported by the blood to the body. The lungs are simpler structures with internal subdivisions. |
| Mammals | Lungs, the large surface area are increased by the highly folded microstructures called alveoli. There is a rich supply of blood to transport gases to and from the lungs. |
- Outline the transport systems in plants, including:
- Root hair cells
- Xylem
- Phloem
- Stomates and lenticels
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| Root hair cells | Water diffuses from the soil to the cytoplasm of cells by the process of osmosis |
| Xylem | Water enters the xylem from the roots and is transported upwards through the stem to the leaves |
| Phloem | Products of Photosynthesis are transported from the leaves to the rest of the plant |
| Stomates | Allow diffusion of gases, Stomates are usually located on the lower surface of the leaf. |
| Lenticels | Pores on woody stem of plants, gas exchange occurs here. |
- Compare open and closed circulatory systems using one vertebrae and one invertebrae as examples
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| Closed Circulatory System | Consists of a muscular pump that pumps fluid through a closed system of tubes which carry material throughout the body. | Humans have a heart the pumps blood through blood vessels which carry throughout the body. |
| Open Circulatory System | The heart pumps blood through blood vessels which open into interstitial spaces. The haemolymph that bathes the cells is reoxygenated in the heart. | Insects rely on their tracheal system, instead of blood carrying the oxygen. Thus insects do not have to have a fast blood flow. |
