Higher Biology

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Higher Biology

• Cells

Mr G Davidson
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Unicellular Organisms

• Unicellular organisms consist of only one cell
  and include animals and plants.
• In order to survive, these organisms must be able
  to carry out all the functions required for life,
  e.g. gas exchange, feeding, reproduction ,etc.
• Unicellular organisms include yeast, Amoeba,
  Paramecium, Euglena, Pleurococcus, etc.

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Unicellular Organisms
Pleurococcus
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Unicellular Organisms
Amoeba
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Unicellular Organisms
Paramecium
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Unicellular Organisms
Euglena
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Unicellular Organisms

• Amoeba have numerous pseudopodia which are blunt
  projections, and the organism can flow into one
  of these, moving like a leech.
• The amoeba feeds by surrounding food particles
  and engulfing them into food vacuoles where the
  food is broken down by enzymes.

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Unicellular Organisms

• Any undigested food remaining in the vacuole is
  left behind until the vacuole can break through
  the membrane and release it.
• This process is called phagocytosis.

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Phagocytosis
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Tissues

• Multicellular organisms have many cells which are
  organised into tissues to perform a particular
  function.
• Although tissues are adapted to carry out a
  particular function, the cells of the tissue
  often vary e.g. phloem tissue contains sieve
  tubes and companion cells.

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Tissues

• Epithelial tissues are lining tissues which cover
  both internal and external surfaces of organisms.

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Tissues

• A lining tissue often contains more than one type
  of cell e.g. the trachea epithelium contains
  ciliated and goblet cells.
• The tissue is usually called after the
  predominant cell type e.g. ciliated epithelia.

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Tissues

• In ciliated epithelium the free surface has cilia
  which beat rhythmically, enabling them to move
  particles along tubes as in the trachea.

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Ciliated Epithelium
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Tissues

• Columnar epithelium is a tissue with column
  shaped cells.
• This type of tissue is found in the stomach and
  small intestine linings.
• The microvilli (s. microvillus) greatly increase
  the surface area to allow for efficient
  absorption of soluble molecules.

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Columnar Epithelium
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Tissues

• Glandular epithelium is made up of cells which
  secrete substances e.g. enzymes, mucus and
  hormones.
• These cells are often clumped together to form
  the glands of the body.

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Glandular Epithelium
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Plant Tissues

• Xylem tissue is composed of
• xylem vessels which offer strength
• tracheids whose cells overlap at the ends and
  they transport water as well as provide support.
• Xylem tissue has lignin impregnated walls which
  provide support.

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Plant Tissues

• Phloem tissue is composed of
• sieve tubes which transport soluble
  carbohydrates
• companion cells which control the sieve tubes.

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Xylem Tissue
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Phloem Tissue
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Cell Ultrastructure
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Cell Ultrastructure

• The ultrastructure of a cell is made up of cell
  organelles which can be seen with the increased
  power of the electron microscope.

Plant Cell
Animal Cell
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Cell Ultrastructure
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Cell Ultrastructure