A Local Ecosystem

PATTERNS IN NATURE

OUTLINE THE HISTORICAL DEVELOPMEMT OF THE CELL THEORY, IN PARTICULAR, THE CONTRIBUTIONS OF ROBERT HOOKE AND ROBERT BROWNIn 1665 Robert Hooke observed cork cells using a compound microscope and described "little boxes or cells distinct from one another"In 1831 Robert Brown observed the necleus in plant and animal cells.

CELL THEORY:--> cells are the smallest units of life (Schwann, Schleiden 1839)--> All living things are made up of cells (Schwann, Schleiden 1839)--> all cells come from pre existing cells (Rudolf Virchow 1839EVIDENCE TO SUPPORT CELL THEORYRobert Hooke’s observation of cork cells, and Leeuwenhoek’s observations of many types of unicellular cells proved that living things were made up of cells Walter Flemming’s observation of cell division – mitosis – proved that cells come from pre-existing cells Supported more as more people began to observe cells and their processes DISCUSS THE SIGNIFICANCE OF TECHNOLIGICAL ADVANCES TO DEVELOPMENTS IN THE CELL THEORY Technological advances have added to our knowledge of cells Staining techniques had an ability to cut thing sections of tissues from multi-cellular organisms revealed cell structures Different coloured dyes are taken up by different organelles, which allows for easy identification of organelles Electron microscope (1933) allowed for more detailed observations Laser scanning and use of 3D imaging software have improved our knowledge X-ray microscopes allow the shape and structure of biological molecules to be identified

IDENTIFY THE MAJOR GROUPS OF SUBSTANCE FOUND IN LIVING CELLS AND THEIR USES IN CELL ACTIVITIES Organic compounds: Contain carbon and are large molecules. The main ones found in cells are; proteins, carbohydrates, lipids and nucleic acids Inorganic compounds: Do not contain carbon and are found in living and non-living things. They include; mineral salts, water, oxygen, carbon dioxide, sodium and potassium

WATER - H2O - Solvent for many substance - Participates in reactions - Stabilises temperature within cells - Involved in the transport of substances within and between cells SODUIM CHLORIDE  - NaCl - Involved in control of water cells - Operation of cell membranes - Helps in the function of nerve and muscle cells CARBON DIOXIDE - CO2 - Used by almost all cells in process of respiration NUCLEIC ACIDS (Nitrogen, Phosphorus, Carbon and Hydrogen) - DNA: Stores genetic material, which defines the structure and function of cell, DNA is in most chromosomes - RNA: Involved in transferring information from chromosomes ribosomes and in using transferred info to construct proteins PROTEINS(Carbon, Hydrogen, Oxygen, Nitrogen)- Contribute to cell structures such as membranes- Composed of ‘building blocks’ – amino acids, which have a complex 3D structure

CARBOHYDRATES(Carbon, Hydrogen, Oxygen and Nitrogen)“Hydrates of Carbon”- Simple Sugars (Monosaccharides): Such as glucose, fructose and galactose are ‘building blocks’ for more complex materials. Glucose is used in respiration and photosynthesis- Double Sugars (Disaccharides): Such as sucrose, lactose and maltose are the ‘building blocks’ and are often transported between cells- Complex Sugars (Polysaccharides): Such as starch, glycogen and cellulose are energy (starch in plants and glycogen in animals) and for cell structure in cell wallsLIPIDS(Carbon, Hydrogen, Oxygen and sometimes Nitrogen)- Fats and oils: Store energy, made from glycerol and fatty acids and are saturated or unsaturated- Waxes: Contribute to structure, eg. of the cell wall, made from acids and molecules larger than glycerol- Phospholipids: Important in structure of membrane, made from fatty acids, Phosphorus and Nitrogen- Steroids: Such as vitamins and hormones are involved in reactions and are needed for structures such as membranesOXYGEN- Used by almost all cells in process of respiration

DESCRIBE THE CURRENT MODEL OF MEMBRANE STRUCTURE AND EXPLAIN HOW IT ACCOUNTS FOR THE MOVEMENT OF SOME SUBSTANCES INTO AND OUT OF CELLS FLUID MOSAIC MODEL: Cell membrane is composed of two layers of phospholipids Phospholipids have hydrophilic (water loving/dissolving) within the layers, and hydrophobic (water hating/repelling) on outside of layers  Proteins are scattered throughout the lipid bilayer, and are capable of movement within the layer, and are responsible for movement of water soluble molecules This structure account for the way the membranes allows of prevent materials to move across

COMPARE THE PROCESSES OF DIFFUSION AND OSMOSIS Diffusion: Is when particles move around to create and equilibrium Diffusion can occur across a barrier such as a membrane if; There is a concentration gradient (difference in concentration) The membrane is permeable (cell membranes are semi-permeable) A form of passive transport (no energy is required)   Osmosis: Is a special form of passive transport involving the diffusion of water molecules across a selectively permeable membrane Water is said to move down and osmotic gradient Two solutions of the same concentration are isotonic The more concentrated solution is called hypertonic The less concentrated solution is called hypotonic Comparison of Diffusion and Osmosis SIMILARITIES; Both involve the movement of substances from a region of high concentration to a region of low concentration Both are passive transport Substances move down the concentration gradient DIFFERENCES; Diffusion is the movement of any substance, whereas osmosis is the movement of water only Osmosis refers to the movement of water over a membrane, whereas diffusion does not have to be across a membrane

SURFACE AREA TO VOLUME RATIOCells are microscopic because it provides a large surface area to volume ratio, which allows efficient exchange of substances across the membrane As the cell increases in size the surface area to volume ration decreases, making the movement of substances less efficient The capacity to take in nutrients and lose waste decreases as the cell grows When a cell reaches a certain size it divides into 2 smaller cells restoring a more favourable surface area to volume areaCell stops growing when its surface area is insufficient to meet the demands of the cell volume.It must divide through the process of mitosis

EXAMPLES THAT DEMONSTRATE THE STRUCTURAL AND FUNCTIONAL RELATIONSHIPS BETWEEN CELLS, TISSUES, ORGANS AND ORGAN SYSTEMS INTO MULTICELLULAR ORGANISMS In multicellular organisms different cells become specialised to perform different functions Cells that are similar in structure and function and are grouped together are called tissues Groups of tissues make up organs and organs make up systems. Eg. Muscle cells --> muscle tissue --> small intestine -->  digestive system Cell --> tissue --> organ --> system

AUTOTROPHS AND HETEROTROPHS IN TERMS OF NUTRIENT REQUIREMENTS Autotrophs are organisms which are capable of synthesising organic compounds from simple inorganic substances --> plant cells are able to synthesise by photosynthesis Heterotrophs are unable to synthesise their organic compounds from simple inorganic substances --> must obtain the substances they need from their external environment-->ultimately rely on the ability of autotrophs to synthesise inorganic material

MATERIALS REQUIRED FOR PHOTOSYNTHESIS AND ITS ROLE IN ECOSYSTEMS

Collaboration in Science: the importance of the contributions of Hooke and Brown: • Cell theory is today attributed to both Shleiden and Schwann and significance is given to the work of previous scientists such as Hooke and Brown It is noticeable that, - collaborative work between scientists, as well as their building on the work of previous scientists, that leads to a new theory in science

Chemicals Found in cells:  • Cells contain organic compounds and inorganic compounds. • Organic compounds contain carbon atoms combined with other atoms. • Inorganic compounds do not necessarily contain carbon atoms. The main inorganic compounds found in cells are water, salts and oxygen. • The main groups of organic compounds found in cells are              --> proteins              --> carbohydrates             --> lipids             --> nucleic acid • Proteins contain the elements carbon, hydrogen, oxygen, nitrogen and sometimes phosphorous and sulfur. Proteins are used for the growth and repair of body tissues, and are present in hormones, cell membranes and enzymes. Enzymes are a vital cellular component, as they help to control all the chemical reactions that occur in the cell. Proteins are composed of chains of amino acids joined together by peptide bonds. • Carbohydrates contain the elements carbon, hydrogen and oxygen, and are the major source of proteins, carbohydrates, lipids, and nucleic acids energy for the cell. The form in which carbohydrates are used by the cell for respiration. • Disaccharides such as sucrose are composed of two sugar units, and are often the form in which sugars are transported in the phloem cells of plants. • Polysaccharides consist of many glucose units joined together, and are used as energy storage molecules. In plants, the polysaccharide starch is used to store energy, and in animals the polysaccharide glycogen is used as an energy storage molecule. • Carbohydrates are also used to provide structural support; structural carbohydrates include cellulose, the main component of cell walls in plants, and chitin, which is found in the exoskeleton of insects and the cell walls of fungi. • Lipids include oils, fats, steroids and waxes. As in carbohydrates, all lipids contain carbon, hydrogen and oxygen, but there is less oxygen in lipids. • Fats consist of a glycerol molecule joined to three fatty acid groups, and are used to store energy. Oils are also used to store energy. • Steroids are present in membranes and sex hormones, and waxes act as a waterproof layer in the leaves and fruits of plants. • Nucleic acids contain a ribose or deoxyribose sugar, nitrogen bases and phosphate groups. They are the main component of DNA, the molecule responsible for heredity in all organisms, and RNA, which is involved in the manufacture of proteins. 

MOVEMENT OF MOLECULES IN AND OUT OF CELLSFor any cell to function it must interact with its surrounding environment and with the cells which surround it. • Substances required by cells for their functioning need to move into cells and waste substances need to pass out of cells. • These substances enter or exit cells through the cell membrane. Substances that enter and leave cells: • Substances needed by cells are gases (oxygen and carbon dioxide), nutrients (sugars, amino acids, glycerol and fatty acids) and water, the main solvent in cells, as well as mineral salts dissolved in water. • Substances that must leave cells are wastes (urea, uric acid and excess carbon dioxide) and products secreted by cells that may be needed to coat the outside of cells (e.g. mucus) or may pass to other cells (e.g. hormones) Glucose has the formula C6H12O6, and is the smallest carbohydrate units are also referred to as monosaccharides, and include the ribose, fructose and glucose molecules

Identify mitosis as a process of nuclear division and explain it’s role Mitosis is the process of cell division whereby certain cells undergo a single nuclear division to produce two genetically identical daughter cells. It’s role is to develop new cell tissue which replace those that have become damaged in some form. This form of nuclear division only occurs in multicellular organisms such as mammals and plants. All body cells undergo the process of mitosis to replace the cells. Each cell that is produced is identical to the parent cell in terms of number of chromosomes (46 in humans) There are 5 steps involved; 1. Interphase: - Cells may appear inactive but the organisms are carrying out it’s functions to maintain life - Chromosomes are becoming visible - DNA replicates 2. Prophase: - Chromatin material shortens and thickens, separating out into individual chromosomes - Each chromosome contains two copies of the DNA - Nuclear membrane begins to break down and is no longer visible. 3. Metaphase: - Chromosomes attach to spindle fibres by a centromere - Centromere divides horizontally 4. Anaphase: - Spindle fibres contract and daughter chromosomes begin to separate 5. Telophase: - Spindle breaks down and daughter chromatids gather at opposite poles of the cell - Nuclear membrane and nucleolus reappear

Explain the need for cytokinesis in cell division Cytokinesis occurs in the final stage of mitosis - the Telophase. Cytokinesis is when the cytoplasm divides and a new nuclear membrane forms around the chromosomes. It is the division of the cytoplasm and begins when the nucleus is completing it’s division. Cytokinesis is important in cell division as it separates the newly formed daughter nuclei. The new nuclear membrane formed on each of the new daughter cells ensures that the cells are completely divided, and are identical to each other and to the parent cell.

Identify that nuclei, mitochondria and chloroplasts contain DNA When cytoplasm divides, the organelles (e.g. mitochondria, chloroplasts and nuclei) are distributed to the daughter cells in equal numbers. It is necessary for the organelles in the cytoplasm to replicate so that they are not reduced in quantity. Mitochondria and chloroplasts contain their ownsmall amounts of DNA so that they are able to replicate themselves during division. By the time the daughter cells are fully grown, they have similar numbers of organelles as the parent cell did.

A Local Ecosystem

Factors determining the distribution and abundance of a species in each environment -Abiotic and biotic factors play a very important role on the abundance of a species in each environment. - In terrestrial environments, abiotic factors such as sunlight, temperature range and water availability are the most influential on a species’ abundance and distribution. - Most species can only live in an area that has certain abiotic criteria, such as how hot the temperature reaches and how dense the soil is. - In aquatic environments, the main abiotic factor affecting the abundance and distribution is the type of environment - saltwater or freshwater. - Organisms such as mangroves and saltmarshes live in areas or high salinity, whereas the casurina cannot survive in the saltwater. - Main biotic features that affect both environments is the availability and abundance of food, number of competitors, mates and predators. - Increase in the number of prey means more food available, resulting in a decrease of prey population.

How to Measure Abundance: - Quadrat method: • The amount of a certain organism are counted within a 1x1m quadrat. • An average number of organisms are taken to estimate the number and abundance. • Often used to measure organisms that stay in the same area. E.g plants, crab holes. - Mark and Recapture: • An organism is marked and monitored over a period of time, returned to their environment, then finally re-captured. • Used to identify abundance of species that are constantly on the move e.g. whales, lions etc. How to measure Distribution: - Transect: • A measurement taken of part of an ecosystem. • A section of an area is recorded to measure the distribution (where the organisms are found in an ecosystem) and any trends.

Photosynthesis and Respiration in ecosystems Photosynthesis: - Process in which plants use the energy from the sun to convert Carbon Dioxide and water to glucose and oxygen. - Plants take in CO2 via their leaves, and water through the roots - Most of the glucose is used for plant growth or reproduction 1- Plants use photosynthesis, and are responsible for storing sunlight energy for use in the ecosystem. Their role as produces starts the food chain and pass on the sun’s energy to consumers.Formula= carbon dioxide + water --> glucose + oxygen Respiration: - Takes place in the mitochondria of all living cells, and results in the release of energy for organisms to use. - Energy in the form of ATP is released and used for cell growth, repair an maintenance. - Role is respiration is to remove oxygen from air, return carbon dioxide to air and provide energyFormula = Glucose + Oxygen --> Carbon Dioxide + Water + Energy

Abiotic and Biotic VariablesAbiotic features: The non-living factors or features of an environment (physical and chemical properties i.e. temperature, pH level, rainfall) Biotic features: The living components or biological features (plants/animals and other organisms)

ROLES AND RELATIONSHIPS BETWEEN ORGANISMSAllelopathy: Is the productions by a plant of specific chemicals that can be detrimental or beneficial to another Parasite: An organism, which obtains its food from a host. The host may be harmed but may not die Symbiosis: Is a type of interaction between organisms where two different species live together in close association Commensalism: A relationship that benefits one species but does not harm the other Mutualism: A relationship where both species benefit

TROPHIC INTERACTIONS Trophic Interaction: Feeding relationship between organisms Trophic Level: Feeding level of an organism In a natural environment, energy from sunlight enters through the process of photosynthesis then flows onto other organisms via food chains and webs. Photosynthesis can change the sun’s energy into chemical energy for other organisms. Food Chains A food chain illustrates what organisms eat what; the arrows indicate “is eaten by” and usually the food chain starts off with a producer. Food Webs A food web is many food chains joined together; it shows the trophic interactions, energy flow of all living things in an ecosystem. Producer: an organism that makes its own food, autotrophs Consumer: an organism that feeds on another living thing, heterotrophs Herbivore: a consumer that only feeds on plant material Carnivore: a consumer that only feeds on animals Biomass Pyramid Biomass: The measure of the mass of all organisms at a particular trophic level In each transfer of energy about 90% is lost as heat and 10% is transferred to the consumer.

ADAPTATIONS IN AN ENVIRONMENT Adaptations can be defined as any feature of an organism that increases its chance of survival in the environment in which it lives These features are built up over a long period of time through natural selection There are 3 types of adaptations; Physiological: Are metabolic features of an organism that help an organism survive – eg; fish produce mucus on the outside of their body to allow water to flow over it easily Behavioural: Things that an organism does to assist its survival – eg; animals curl up into a ball when cold to decrease surface area Structural: Anatomical/structural features that assist survival –eg; stream line shape in fish

HUMAN IMPACT ON ECOSYSTEMSLand clearance and habitat destruction Erosion and loss of soil Salination and desertification Pollution of air, water and soil Fertilisers and pesticides Loss of biological diversity Exploitation and depletion of natural, non-renewable resources Production of poisonous materials Introduction of new/foreign species of flora and fauna

PREDATOR & PREY POPULATIONS Factors that affect numbers in predator and prey populations in the area studied = - Number of predators competing for the same prey (ration between predators and prey)- Availability of prey’s food - Birth and death rate of prey (includes ratio of males and female organisms) - number of prey - Size of ecosystem for supporting the predator and prey numbers - Movement between ecosystems - Number of shelter sites available

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