The Nature and Variety of Living Organisms

• Characteristics of all living organisms

  • Movement
  • Respiration
  • Sensitivity
  • Control
  • Growth
  • Reproduction
  • Excretion
  • Nutrition
• Why is energy necessary?

  • Energy is necessary to carry out life processes e.g. movement, respiration and excretion
• What is nutrition in plants?

  • Plants use sunlight, carbon dioxide and water to produce oxygenand glucose in the process of photosynthesis
  • Because plants create their own food for energy, they are described as being autotrophic
• What is nutrition in animals?

  • Animals consume other living organisms in order to obtain the energy they require
  • They break down larger complex molecules into simpler molecules through the process of digestion
  • As animals obtain their food from a range of different sources, they are described as being heterotrophic
• Differences between autotroph and heterotroph 


  The differences are..

  
• What is respiration?

  • Respiration is a chemical reaction carried out in all living organisms
  • Energy is released from glucose either in the presence of oxygen (aerobic respiration) or the absence of oxygen (anaerobic respiration)
  • The reactions ultimately result in the production of carbon dioxideand water as waste products
  • Energy is transferred in the form of ATP
• What is excretion?

  • Chemical reactions that take place inside living cells are described as metabolic reactions
  • Metabolic reactions produce waste products, some of which may be toxic
  • These toxic products must be eliminated from the body
  • Excretion is the removal of toxic materials and substances from organisms
• What is excretion in animals?

  • Waste products excreted by animals include:
  • Carbon dioxide from respiration
  • Water from respiration and other chemical reactions
  • Urea which contains nitrogen resulting from the breakdown of proteins

  
• What is excretion in plants?

  • Waste products excreted by plants include:
  • Oxygen from photosynthesis
  • Carbon dioxide from respiration
  • Water from respiration and other chemical reactions

  
• Why do living organism respond to surroundings?

  • The sensitivity of an organism refers to its ability to detect and respond to stimuli in its surroundings
  • Responding to the environment around them gives an organism the best chances of survival
• What are sensitivity responses for animals?

  • In humans, the nervous system provides a complex system of receptors, neurones and effectors which detect and respond to different stimuli using electrical impulses
  • The endocrine system also allows a response to stimuli using chemical messengers, which travel in the blood, called hormones

  
• What are sensitivity responses in plants?

  • In plants, responses are controlled by chemicals and are usually much slower
  • Geotropism describes a plants response to gravity which causes the roots to grow down into the soil
  • Phototropism describes a plant's response to light which causes shoots to grow towards sunlight

  
• What is movement in a living organism?

  • Movement is an action by an organism causing a change of position or place
  • The movement of an organism from place to place is called locomotion
  • Plants cannot move from place to place but can change their orientation
  • For example, sunflowers track the sun and so change their orientation throughout the day
• What is control in living organisms?

  • Living organisms must control their internal environment in order to keep conditions within required limits
• Homeostasis in humans

  • Thermoregulation refers to the control of body temperature
  • The optimum human body temperature is 37°C
  • If body temperature increases e.g. during exercise, mechanisms for control will be initiated to return the temperature back to the optimum
  • Mechanisms include sweating or vasodilation
  • Other homeostatic mechanisms in humans include glucoregulation(control of blood glucose levels) and osmoregulation (control of water levels)

  
• Homeostasis in plants

  • Plants use transpiration to maintain a suitable temperature
  • Water evaporates from the stomata on the underside of the leaf, leading to heat loss

  
• What is reproduction?

  • Reproduction is the process that leads to the production of more of the same kind of organism
  • Reproduction is fundamental to the survival of a population and ultimately, the species
  • There are different types of reproduction: sexual and asexual
• What is sexual reproduction?

  • In this type of reproduction, the male and female gametes fuse together
  • In humans, the male gamete is the sperm and the female gamete is the egg
  • In plants, the male gamete is in the pollen grains and the female gamete is the ovule
  • The DNA of the offspring is composed of both maternal and paternal DNA

  
• What is asexual reproduction?


  • Cells or whole organisms can also reproduce using asexual reproduction
  • Mitosis is an example of asexual reproduction
  • There is only one parent involved so an exact clone is produced
  • The DNA of offspring is identical to parental DNA
  • Plants can reproduce asexually through tubers, budding or runners
  • Single-celled organisms such as bacteria or amoebareproduce asexually

  
• What is growth in living organisms?

  • Growth is defined as a permanent increase in size
  • In animals, an individual grows larger between the zygote and adultstage with changes in proportion or shape
  • In plants, an individual grows larger throughout their whole life withnew shoots, leaves, branches etc forming year after year
• What are the five kingdoms of living organism?

  • Animals
  • Plants
  • Fungi
  • Protoctists
  • Prokaryotes
• What can the first four kingdoms be called?

  • The first four kingdoms in this list (the animals, plants, fungi and protoctists) can actually be grouped together, as they are all eukaryotic organisms (also known as eukaryotes)

  
• What are eukaryotic organisms?

  • Eukaryotic organisms can be multicellular or single-celled and are made up of cells that contain a nucleus with a distinct membrane

  
• What are prokaryotic organisms?


  • Prokaryotic organisms (also known as prokaryotes) are in a separate kingdom and are different from eukaryotes as they are always single-celled and do not contain a nucleus (instead, the nuclear material of prokaryotic cells is found in the cytoplasm)
  • Bacteria are prokaryotic organisms
  • Prokaryotic cells are substantially smaller than eukaryotic cells
• What are the main features of animals?

  • They are multicellular
  • Their cells contain a nucleus with a distinct membrane
  • Their cells do not have cellulose cell walls
  • Their cells do not contain chloroplasts (so they are unable to carry out photosynthesis)
  • They feed on organic substances made by other living things
  • They often store carbohydrates as glycogen
  • They usually have nervous coordination
  • They are able to move from place to place

  
• What are some cell structures found in both animals and plants?


  They are..

  
• What are the main features of a plant?

  • They are multicellular
  • Their cells contain a nucleus with a distinct membrane
  • Their cells have cell walls made out of cellulose
  • Their cells contain chloroplasts (so they can carry out photosynthesis)
  • They feed by photosynthesis
  • They store carbohydrates as starch or sucrose
  • They do not have nervous coordination

  
• What are some cell structures only found in plants?

  They are..

  
• Fungi


  • Usually multicellular but some are single-celled (e.g. yeast)
  • Multicellular fungi are mainly made up of thread-like structures known as hyphae that contain many nuclei and are organised into a network known as a mycelium
  • Their cells contain a nucleus with a distinct membrane
  • Their cells have cell walls made of chitin (chitinous cell walls)
  • Their cells do not contain chloroplasts (so they cannot carry out photosynthesis)
  • They feed by secreting extracellular digestive enzymes(outside the mycelium) onto the food (usually decaying organic matter) and then absorbing the digested molecules. This method of feeding is known as saprotrophic nutrition
  • Some fungi are parasitic and feed on living material
  • Some fungi store carbohydrates as glycogen
  • They do not have nervous coordination
• Fungi


  • moulds
  • mushrooms
  • yeasts
• What does a fungi cell look like?


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• Protoctists


  A very diverse kingdom of organisms that don't really belong in any of the other eukaryotic kingdoms (animals, plants and fungi)
• Protoctists


  • Mainly microscopic and single-celled
  • Some aggregate (group together) into larger forms, such as colonies or chains of cells that form filaments
  • Their cells contain a nucleus with a distinct membrane
  • Some have features making them more like animal cells e.g. Plasmodium (the protoctist that causes malaria)
  • Some have features, such as cell walls and chloroplasts, making them more like plant cells e.g. green algae, such as Chlorella
  • Some photosynthesise and some feed on organic substances made by other living things
  • They do not have nervous coordination
• Protoctists

  • amoeba
  • Paramecium
  • Plasmodium
  • Chlorella
• What does a protoctist? 


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• How are prokaryotes different from other living organisms?

  • The prokaryotes are different from the other four kingdoms (which are all eukaryotes) as prokaryotic organisms are always single-celled and do not contain a nucleus
  • Instead, the nuclear material of prokaryotic cells is found in the cytoplasm
• What are the main characteristics of bacteria?

  • They are microscopic single-celled organisms
  • They have a cell wall (not made of cellulose), cell membrane, cytoplasm and plasmids
  • They lack a nucleus but contain a circular chromosome of DNA
  • They lack mitochondria and other membrane-bound organelles found in eukaryotic cells
• What are some examples of bacteria?

  • Lactobacillus (a rod-shaped bacterium used in the production of yoghurt from milk)
  • Pneumococcus (a spherical bacterium that acts as the pathogen causing pneumonia)
• How do bacteria feed?

  • Some bacteria can carry out photosynthesis despite having no chloroplasts. This is because they still possess chlorophyl and enzymes necessary to synthesize sugars from carbon dioxide.
  • Most feed on other living or dead organisms (if they feed on dead organic matter then they are known as saprobionts or decomposers)
• What does a bacteria cell look like?


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