Ch. 2 - Living Things and Cells

• Organism

  A living thing
• Cells

  The basic building blocks of living things, (living things are made of cells)
• Nutrition

  the way in which living things get their food
• Excretion

  The way in which living things get rid of waste that they produce
• Response

  The way in which living things react to changes in their surroundings
• Reproduction

  The way in which living things produce new living things
• There are 5 major groups of living things
• Groups of living things

  • Bacteria
  • Fungi
  • Plants
  • Animals
  • Others (Protists)
• Bacteria

  • Tiny microscopic living things. Some cause disease, some cause decay, some are used to produce valuable substances
• Fungi

  • Mushrooms, moulds and yeast
• Plants

  • Trees, grasses, flowers
• Vertebrate

  Animals that have backbones
• Animals

  • Humans, fish, insects
• Invertebrates

  Animals that do not have backbones
• Others (Protists)

  • Seaweeds, amoeba
• Examples of Vertebrates

  • Horse
  • Seagull
  • Frog
  • Snake
• Examples of Invertebrates

  • Spider
  • Earthworm
  • Fly
  • Jellyfish
• Biodiversity 


  The range of living things
• Each living thing needs special conditions in which to grow. Unfortunately, many of these conditions are being lost due to human activities, for example:

  • Woodlands are being destroyed for housing and roads
  • Forests are being lost to supply wood for building
  • Lakes are destroyed by pollution
• Animal cells

  • cell membrane
  • nucleus
  • cytoplasm
• Cell Membrane - Animals

  The cell membrane is a very thin layer that surrounds the cell.

  Its function (i.e. what it does) is to hold the cell contents in place and control what passes into and out of the cell.

  For example:

  • When we exercise, our muscle cells allow glucose and oxygen to pass in from our blood vessels to supply energy to the cells.
  • Wastes can pass out into the blood through our cell membranes so that we can remove the waste from our bodies.
• Nucleus - Animals

  The nucleus is normally round.

  Its function is to act as the control centre of the cell.

  The nucleus controls the cell by means of strands called chromosomes. Each chromosome has many genes.

  Each gene is made of DNA and controls one particular feature or characteristic. These features or characteristics are passed on (or inherited) from parents to their children. For example, humans have genes to control features such as eye colour, the formation of nails, height and the formation of fingers and toes.
• Cytoplasm - Animals

  Cytoplasm is a watery liquid found between the nucleus and the cell membrane.

  Its functions are to carry out some cell reactions and to support tiny cell structures.

  These structures carry out many of the vital processes of the cell. They are too small to be seen using a light microscope.

  One such structure is the mitochondrion (plural mitochondria). These tiny structures supply energy to the cell.
• Plant Cells

  • cell wall
  • cell membrane
  • nucleus
  • cytoplasm
  • vacuole
• Cell Wall - Plants

  A cell wall is found outside the cell membrane in plant cells.

  The function of the cell wall is to give strength to the plant cell. This is needed as plants, unlike many animals, do not have strong skeletons. The cell walls make plant cells stronger and less flexible than animal cells.

  The material in cell walls is called cellulose. This forms everyday substances such as paper, cardboard and cotton.
• Cell membrane - Plants

  Plant cell membranes are similar to animal cell membranes
• Nucleus - Plants

  The nucleus is almost the same in plant and animal cells. However, the genes present in plant cells are different from those found in animal cells.

  For example, plant cells have genes for features such as forming a cell wall and making the green chemical (chlorophyll) found in many plant cells.
• Cytoplasm - Plants

  The cytoplasm in plant cells is similar to cytoplasm in animal cells. However, plant cytoplasm may contain tiny green structures (chloroplasts), which allow the plant to make its own food in a process called photosynthesis.
• Vacuole

  A vacuole contains liquid. If the vacuole is full of liquid, it forces the cytoplasm to push out against the cell wall.

  In this way the function of the vacuole is to give strength to the cell. Normally vacuoles cannot be seen using a light microscope.
• Function and Location of Cell Structures

  
• The Light Microscope

  A microscope is used to view objects that are too small to be seen by eyesight alone.

  The term 'magnification' means how many times larger the object appears to be when viewed under the microscope.
• Eyepiece Lens

  The eyepiece is the lens that is nearest to your eye. If it is marked ×10 it makes the object tan times larger (that is, it magnifies the object by ten).
• Objective Lens

  Each objective lens has a different magnification. The total magnification is found by multiplying the powers of the eyepiece and objective lenses being used.

  For example: An eyepiece marked ×10 and an objective lens marked ×20 will give a total magnification of ×200.

  power of eyepiece x power of objective lens = total magnification
• Nosepiece

  The nosepiece can rotate to move the different objective lenses into position.
• Stage

  The stage is used to support the microscope slide. It has a hole in the centre to allow light to pass through.
• Clips

  The clips are used to hold the microscope slide in place.
• Mirror or light

  The mirror is used to reflect light from a lamp up through the object. Some microscopes have a light instead of a mirror.