Patterns in Nature Summary free essay sample

Organisms are made of cells that have similar structural characteristics * Outline the historical development of the cell theory, in particular the contributions of Robert Hooke and Robert Brown Robert Hooke was the first person to observe a cell through a compound microscope in 1665. Franscesco Redi used a microscope to observe that flies do not spontaneously appear but develop from eggs laid by other flies. Many years later, Robert Brown observed a large body in both animal and plant cells that he named the nucleus. M. Schleiden and T. Schwann came up with the first two points of cell theory; 1. Cells are the smallest units of life and 2. All living things consist of one or more organised structures called cells. Rudolf Virchow later added the third point to the cell theory; 3. All living things arise from pre-existing cells. * Describe evidence to supports the cell theory * Discuss the significance of technological advances to developments in the cell theory Identify cell organelles seen with current light and electron microscopes In light microscopes the organelles that could be seen were cell wall, cytoplasm, nucleus, nucleolus, chloroplast, water vacuole and cell membrane. * Describe the relationship between the structure of cell organelles and their function 2. Membranes around cells provide separation from and links with the external environment * Identify the major groups of substances found in living cells and their uses in cell activities The major group of substances found in living cells are carbohydrates, lipids, proteins and nucleic acids. Carbohydrates are used as nutrients for cells, cellular respiration, provide energy for the body to function and live off, give structure to cell walls and store glucose. Lipids are a structural component of cell membrane and modulator of cell activity. Proteins regulate the immune system and signal pathways. Nucleic acids are used for the growth repair and reproduction of cells and are also used in DNA and RNA. * Identify that there is movement of molecules into and out of cells Passive transport is the movement of molecules across the cell that doesn’t require expenditure of energy. Active transport on the other hand is the movement of molecules across cell membranes requiring energy and proteins that act as carriers * Describe the current model of membrane structure and explain how it accounts for the movement of some substances into and out of cells The cell membrane is mainly composed of integral proteins and lipid bilayer. The phospholipids form a bilayer with the hydrophilic head facing outwards and the hydrophobic tails facing inwards. This model for the cell membrane is called the fluid mosaic model. The fluid mosaic model demonstrates the semi permeable nature of membrane. Polar molecules have trouble passing though non-polar parts of the membrane but can easily pass through the polar parts of the membrane, therefore to move through the membrane they require protein channels to provide a path through it. Water molecules pass through pores in the lipid and protein channels allow certain substances pass through the membrane; once the molecule enters the protein channel; the protein undergoes a conformational change so that the molecule can pass through. Compare the processes of diffusion and osmosis Diffusion is the movement of molecules from an area of high concentration to an area of low concentration whereas osmosis is the movement of water across a semi-permeable membrane from an area of high concentration to an area of low concentration; they both use passive transport * Explain how the surface area to volume ratio affects the rate of movement of substances into and out of ce lls All nutrients and gases needed by a cell have to pass across the cell membrane as do all waste materials when leaving the cell. The requirements of a cell can quickly outstrip the rate at which the membrane can let material cross. As a cell increases in size, it would require greater amounts of nutrients and would have to excrete more waste, the surface area would increase but at a much slower rate. 3. Plants and animals have specialised structures to obtain nutrients from their environment * Identify some examples that demonstrate the structural and functional relationships between cells, tissues, organs and organ systems in multicellular organisms * Cells gt; Tissues gt; Organ gt; System gt; Organism * E. g. Muscle cell gt; Muscle Tissue gt; Stomach gt; Digestive system gt; Human * Distinguish between autotrophs and heterotrophs in terms of nutrient requirements * Plant cells are autotrophic and obtain energy through photosynthesis * Animal cells are heterotrophic and obtain energy through consuming other organisms * Identify the materials required for photosynthesis and its role in ecosystems * Carbon dioxide, water, energy from sunlight, chlorophyll * Photosynthesis occurs only when plants can obtain carbon dioxide, water and light from their external environment, products produced are glucose and oxygen. All living things depend on photosynthesis. Photosynthesis enables green plants to obtain energy directly; plants and animals obtain this energy indirectly from the food they eat. * Identify the general word equation for photosynthesis and outline this as a summary of a chain of biochemical reactions * Carbon dioxide + water light energy gt; glucose + oxygen 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 * Water and minerals are obtained through root systems; root systems must have a very large surface area to absorb enough nutrients for the whole plant, they achieve this through having a branching structure and many root hairs. The root system can also be used to anchor the plant. Tap roots: these types of root systems have one main root, called the tap root, side roots come grow out from the tap root, tap roots many penetrate deeply into the soil; sometimes the taproots act as storage organs. * Fibrous roots: these root systems form networks of roots close to the soil surface, they can spread out widely to support the plant, and provide a large surface area for absorption of mineral ions and water * Aerial roots: in areas like water logged estuaries or swamps, plants produce roots that grow above the ground, these roots help with gas exchange. Explain the relationship between the shape of leaves, the distribution of tissues in them and their role * Leaves that don’t get as much sunlight usually have flat, broad leaves to maximise the area exposed to sunlight which allows them to photosynthesise more. Palisade mesophyll contains large amounts of chloroplasts to increase rate of photosynthesis and are arranged closest to the surface of the leaf that receives the most sunlight. Spongy mesophyll cells are arranged between the palisade mesophyll and the stomata, with gaps or a space between them; the gaps allow air to diffuse among the cells which are producing and release both CO2 and O2; this is where gas exchange occurs. Stomata open and close to limit and increase the rate of gaseous exchange and loss of water. Xylem vessels transport water to photosynthetic cells. Phloem tissues transport products of photosynthesis (sugars). Describe the role of teeth in increasing the surface area of complex foods for exposure to digestive chemicals * The role of teeth in a digestive system is to break large foods into smaller pieces, increasing surface area and allowing larger exposure to digestive chemicals * Explain the relationship between the length and overall complexity of digestive systems of a vertebrate herbivore and a vertebrate carnivore in respect to * The chemical composition of their diet * The functions of the structures involved Carnivores: The main com ponent of their diet is meat. Meat contains protein, carbohydrates and lipid (fat), meat is high in energy, and is relatively easy to digest as animals don’t contain cell walls or cellulose like plants; this means that the digestive systems of carnivores are short compared to herbivores. They have very short large intestines, as the meat has already been absorbed in the small intestine * Herbivores: The main component of a herbivore’s diet is plant material. Plants are composed of glucose, starch, lipids, protein, chloride ions and lignin. As most of the mass of plant material is made up of cellulose it is difficult to breakdown compared to animal material, herbivores use the help of micro-organisms to help digest the cellulose. This digestion can occur in two places; fore-gut fermenters digest their food in a chamber before the stomach called the rumen. Hind-gut fermenters digest its food in a chamber after the small intestine called the caecum. The digestive systems of herbivores are a lot larger and longer than that of carnivores. 4. Gaseous exchange and transport systems transfer chemicals through the internal and between the external environments of plants and animals * Compare the roles of respiratory, circulatory and excretory systems * Respiratory System The respiratory system enables gaseous exchange to occur between an organism and its external environment. Organisms take in oxygen which is essential to keep alive and remove carbon dioxide. * Circulatory (transport) System A transport system ensures that all cells in an organism are supplied with necessary nutrients and gases as well as removing waste. The circulatory system transports gases e. g. oxygen and carbon dioxide, nutrients, waste products, hormones and antibodies. It is responsible for maintaining a constant internal environment. The circulatory system also removes any toxins or pathogens and is responsible for the distribution of heat. * Excretory System The excretory system is responsible for removing metabolic wastes from the blood and to expel them from the organism. Two main waste products are: Nitrogenous wastes – excreted as part of urine Carbon dioxide – expelled from the lungs * Identify and compare the gaseous exchange surfaces in an insect, a fish, a frog and a mammal * Insects: Insects have a system of branching tubes within their bodies called tracheae; they are open to the external environment by spiracles (pores). The tracheae branch throughout the tissues of the insect, bringing air directly to the body cells. * Fish: The respiratory system in fish are called gills, the gills have a plentiful blood supply, and so the gases diffuse directly into the blood supply. Diffusion of oxygen in and carbon dioxide out occurs at the same time, as water only flows in one direction. * Frogs: Frogs have two respiratory surfaces: skin and lungs, frogs have a well-developed blood supply to their skin, this enables the diffusion of gases directly through the skin. Oxygen from the air diffuses into the moist skin and is transferred by the blood to the heart, where it is pumped to the rest of the body. * Mammals: The gas exchange organs are the lungs, they are inside the body to prevent drying out. Explain the relationship between the requirements of cells and the need for transport systems in multicellular organisms * Unicellular organisms rely on diffusion to supply requirements such as oxygen, respiration, remove of waste products such as carbon dioxide and other metabolic waste. * Multicellular organisms are larger in size and aren’t able to use osmosis due to their small surface area to volume ratio. Large organisms such as animals need more nutrien ts and produce more waste. A transport system within the bodies of large organisms is able to transport nutrients and dispose of waste efficiently. Outline the transport systems in plants, including: * Root hair cells * Root hairs provide a large surface area for water to diffuse into the plant. Water seeps through the root hairs and travels up the xylem. * Xylem * Xylem consists of dead cells and transports water and mineral ions up the plant stem to the leaves. * Phloem * The phloem transports glucose throughout the plant and allows organic material to be transported up and down the plant. * Stomates and lenticels * Stomates are located on leaves of plants, they are pores in the leaf which enable the diffusion of gases and receive the gases needed for photosynthesis. Stomates can open and close; when open, gas exchange occurs in the leaf and photosynthesis occurs, but when they close, the rate of photosynthesis slows, this is controlled by guard cells, and dependent on light, humidity, water deficiency, and high temperatures. * Lenticels are pores on the woody stems of plants. The gases needed for respiration are diffused through lenticels and allow carbon dioxide to diffuse out. * Compare open and closed circulatory systems using one vertebrate and one invertebrate as examples * Invertebrates such arthropods have open systems. This involves the movement haemolymph around the whole body by a simple pumping system. The fluid is pumped to the front of the animal and slowly flows to the back. The pressure is very low and fluids circulate slowly. An insect has an open circulatory system. The heart contracts and fluid flows to the front of the insect. The fluid flows through the tissues of the body and enters the heart again through a series of holes. The fluid is then pumped again to the rest of the body. * Large animals such as vertebrates and squids have closed systems. The closed circulatory system consists of a muscular pump (heart) that forces blood through a series of tubes (blood vessels), these tubes carry materials rapidly throughout the body. The nutrients, wastes and gases are all carried in blood; the nutrients must first diffuse into lymph before it can be used. Closed systems meet the needs of large active animals. Humans have closed circulatory systems; the heart pumps blood around the body in veins and arteries, the body cells receive nutrients from the blood through the veins. 5. Maintenance of organisms requires growth and repair * Identify mitosis as a process of nuclear division and explain its role * Mitosis is the process where the nucleus divides into two separate nuclei, cytokinesis is the division of the cytoplasm forming two new cells; the role of mitosis is the growth and repair of multicellular organisms. * Identify the sites of mitosis in plants, insects and mammals * The site of mitosis in plants is; the root tip. In insects it is when the larvae undergo metamorphosis into an adult. In mammals mitosis occurs in many places including skin cells, hair cells and nail cells. * Explain the need for cytokinesis in cell division * Cytokinesis usually occurs immediately after mitosis, it is necessary to ensure that chromosome numbers remain constant. * Identify that nuclei, mitochondria and chloroplasts contain DNA * Nuclei contain DNA in the form of chromosomes; they contain genetic information that determines heredity and characteristics * Mitochondria have a set of their own DNA in a ring Chloroplasts also have a circular