notes - the nature and variety of living organisms

Alternative transcript:

to identify and selectively control what enters and leaves the cell Mitochondria: where aerobic respiration reactions occur, providing energy for the cell Ribosomes: carry out protein synthesis; found on the rough endoplasmic reticulum Plants: multicellular organisms - contain chloroplasts (the site of photosynthesis) - chlorophyll within chloroplasts absorb light from the sun cellulose cell walls - provide strength and shape to the cell permanent vacuole - stores cell sap (water, enzymes, salts, sugars, ions) and maintains turgor pressure, providing structural support to the cell store carbohydrates as starch or sucrose - e.g. cereals (maize), herbaceous legumes (peas, beans) Animals: - multicellular organisms cannot photosynthesise - no chloroplasts - no cell walls (only cell membrane) most have a nervous system in order to coordinate movement - often store carbohydrates as glycogen - sometimes have smaller, often temporary, vacuoles to store nutrients and waste e.g. mammals (humans), insects (houseflies, mosquitoes) Fungi: body is usually organised into a mycelium of thread-like structures called hyphae which have many nuclei, but some are single-celled (e.g. Mucor (mould on bread) has a typical hyphal structure, yeast is single-celled) cell walls made of chitin feed by extracellular secretion of digestive enzymes which break food material down so the organic products can be absorbed (saphrotrophic nutrition) cannot photosynthesise many store carbohydrates as glycogen e.g. Mucor, yeast Protoctists: single-celled organisms - some have similar features to animal cells (Amoeba), others like plants (Chlorella) e.g. Plasmodium (causes malaria), Amoeba (lives in pond water), Chlorella (chloroplasts) Prokaryotic organisms Prokaryotes do not have a nucleus or membrane-bound organelles Bacteria microscopic single-celled organisms - have a cell wall, cell membrane, cytoplasm and plasmids - no nucleus (but have circular chromosomes of DNA) - some can photosynthesise, but mainly eat off other organisms (dead or alive) e.g. Lactobacillius bulgaricus (rod-shaped - yoghurt production), Pneumococcus (spherical - causes pneumonia), Salmonella Pathogens Disease-causing organisms - include some fungi, protoctists, bacteria and viruses Viruses - not living organisms - are small (smaller than bacteria) particles parasitic - can only reproduce within living cells, can affect every type of organism hijacks the cell mechanisms to create copies of itself and spreads by cell bursting wide variety of shapes and sizes (no cellular structure) - have a protein coat and one type of nucleic acid (DNA or RNA) e.g. tobacco mosaic virus (causes discolouring of tobacco plant leaves by preventing chloroplast production), influenza, HIV