Transcript Cells - 2011sec1lss

Cells –
division of labour
Recap: Unicellular organisms
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Amoeba – Single cell organism
The same cell has to..
Take in food
Excrete waste
Move
Grow
Reproduce
This is not the case for multi-cellular organisms!
Multicellular organisms
• Different functions required to maintain life processes
are performed by different types of cells
• 200+ types of cells in a human body
• Cells have different shapes and structures suited for their
job
Specialisation – division of labour
– More efficient and effective
– Multitasking!
– Disadvantages?
“Blank” cells?
• Some cells are “blank” because they do not have
particular functions yet, but can later change into nearly
any type of body cells
Stem cells
– Found in embryos, umbilical cord blood, bone marrow
– Umbilical cord blood “bank”
• Potential ACE project
Guard cell
Nerve cell
Sperm cell
Root epidermal cell
Fat cell
Red blood cell
Guard cell
• Occurs in pairs on the underside
of a leaf
• Each pair is shaped so that a tiny
opening called stoma (plural:
stomata) exists between them
• Stomata allows for gaseous
exchange between the leaf and
the surroundings, and water to
escape
• The opening and closing of the
stomata is caused by the guard
cells changing in shape
Sperm cell
• Has to swim towards an egg to
fertilise it
• Has a “tail” called a flagellum to
help it swim
• Has much more mitochondria
(part of the cell that releases
energy) as compared to other cells
• Store fat for future use
• Recent studies have shown that
the number of fat cells do not
decrease when you lose weight –
only the fat cell volume changes.
• “If you are overweight and you
lose weight, you still have the
capacity to store lipids because
you still have the same number of
fat cells. That may be why it’s so
hard to keep the weight off.”
Fat cell
• Multiple nerve endings
• Specialised extensions to receive
messages (dendrites) and send
messages (axons) to other nerve
cells quickly
Nerve cell
• Have long and narrow
protrusions called root hairs
• Large surface area for the
absorption of water and minerals
Root epidermal cell
• Flat and biconcave in shape
• Large surface area : Volume ratio
– allows for rapid diffusion of
gases
• Contains haemoglobin which
carries oxygen
• Absence of nucleus
• Elastic – can squeeze through
narrow capillaries
Red blood cell
Cells –
from cells to tissues
Cells  Tissues
• In multicellular
organisms, cells of the
same type are organised
into groups or layers
called tissues
• They work together to
do the same job
Animal tissues
Nerve cells → nerve tissue
• found in the brain and
spinal cord
• carries messages from one
part of the body to another
Cells  Tissues
• In multicellular
organisms, cells of the
same type are organised
into groups or layers
called tissues
• They work together to
do the same job
Animal tissues
Muscle cells → muscle tissue
• found in the limbs and in
the walls of some organs
• contracts and relaxes to
cause body movements
Cells  Tissues
• In multicellular
organisms, cells of the
same type are organised
into groups or layers
called tissues
• They work together to
do the same job
Animal tissues
Fat, bone, blood, cartilage
cells → Connective tissue
• support and connect
different tissues
• join different parts of an
organism
Cells  Tissues
• Cells of the same type
are organised into
groups or layers called
tissues
• They work together to
do the same job
Epithelial cells → Epithelial
tissue
• protects structures beneath
them
Animal tissues
Cells  Tissues
Vascular
tissue
• found in all
parts of a
plant
• carries food
(phloem) and
water
(xylem) to
various parts
of the plant
Plant tissues
Dermal
tissue
• found on surfaces
of different parts
of a plant
• protects plants
against injury and
drying up
Ground
tissue
• found mainly in the
stems of plants
• supports and
strengthens the plant
Cells –
from tissues to organs
Tissues  Organs
• Different tissues are
usually grouped together
to form an organ
• Tissues in the organ work
together to carry out one
or more functions
• Organs are covered by
epithelial tissues for
protection
Animal organs
Brain
• consists of nerve tissue +
connective tissue
• controls the activities of the
body
Tissues  Organs
• Different tissues are
usually grouped together
to form an organ
• Tissues in the organ work
together to carry out one
or more functions
• Organs are covered by
epithelial tissues for
protection
Animal organs
Stomach
• consists of muscular tissue +
connective tissue
• digests food
Tissues  Organs
• Different tissues are
usually grouped together
to form an organ
• Tissues in the organ work
together to carry out one
or more functions
• Organs are covered by
epithelial tissues for
protection
Animal organs
Heart
• consists of muscular tissue +
connective tissue
• Pumps blood around the
body
Tissues  Organs
• Different tissues are
usually grouped together
to form an organ
• Tissues in the organ work
together to carry out one
or more functions
• Organs are covered by
epithelial tissues for
protection
Animal organs
Lungs
• consists of muscular tissue +
connective tissue
• enables gaseous exchange
between the body and the
surroundings
Roots
Flowers
Leaves
Plant organs
Stems
Cells –
from organs to system
Human organ systems
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respiratory system
circulatory system
nervous system
digestive system
excretory system
skeletal system
reproductive system
Plant organ systems
Shoot system
(above ground)
Root system
(below ground)
Cells –
from system to organism
Different systems make up the
whole organism.
• Each system carries out its own function
• Interacts and works together with other
systems to enable the organism to function
smoothly and efficiently :D
Different systems make up the
whole organism.
Summary
Cell
Tissue
Organ
System
Organism
Digestive System –
Digests food
Division of labour exists
amongst cells, tissues, organs
and systems to ensure the
organism functions properly and
efficiently.