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Biology 1) Nature and Variety of organisms, 2) Levels of organisation,…
Biology
1) Nature and Variety of organisms
1) Characteristics of living organisms
All Living organisms share the same
8 basic characteristics
:
Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition.
Mnemonic: MRS GREN
3) Stem cells
Embryonic stem cells can turn into any type of cell: These are also called undifferentiated cells. They can
change
to
different types of cells
, depending on what
instructions
they're given
Some people are against stem cell research:
This is because they feel that human embryos shouldn't be used for experiments since each one is a human life or has the potential to be a human life
Stem cells may be able to cure many diseases. Stem cells can be transferred from a healthy person to a patient to replace the faulty cells
4) Plants, Animals and Fungi
Plants:
plants are
multicellular
, they have
chloroplasts
which means that they can
photosynthesis
. Their
cell walls
, which are made of
cellulose
. Plants also
store carbohydrates
as
sucrose
or
starch
Animals:
Animals are also
multicellular
. They have some kind of
nervous coordination
, this means that they can respond rapidly to changes in their environment. They can usually
move around
from one place to another. They often
store carbohydrate
in the form of
glycogen
Fungi (Ex: Mushroom & Yeast):
Some are
single-celled
, and others have a
body
called a
mycelium
, which is made up of
hyphae
. The hyphae contain lots of
nuclei
. They
can't photosynthesize
, and their cells have
cells walls
made of
chitin
. Most fungi feed by
saprotrophic nutrition
-- they secrete extracellular enzymes into the area outside their body to dissolve their food, so they can then absorb the nutrients. They can
store carbohydrate
as
glycogen
.
Living organisms are grouped as plants, animals and fungi. These are all Eukaryotic cells
5) Protoctists, Bacteria and Viruses
Protoctists: (ex Chlorella and amoeba)
These are
single-celled
and
microscopic
. Some have
chloroplasts
and are similar to
plant cells
, others are more like
animal cells
Bacteria: (ex Lactobacillus bulgaricus - To make yougart, pneumococcus - round shaped):
These are also
single-celled
and
microscopic
. They
don't
have a
nucleus
but they have a
circular chromosome
of
DNA
. Some can
photosynthesise
, but most bacteria
feed
off other
organisms
-- both living and dead.
Viruses: (ex Influenza, covid, HIV)
These are
particles
, rather than cells and they are
smaller
than bacteria. They can only
reproduce
inside
living cells
, a virus is an example of a
parasite
--- it depends on another organism to grow and reproduce. They
infect all types
of living organisms and they come in loads of
different shapes
and
sizes
. They don't have a cellular structure... however they have a
protein coat
around some
genetic material
Some organisms are Pathogens:
Pathogens
are
organisms
that cause
disease
. They include some
fungi
,
protoctists
and
bacteria
.
Viruses
are also pathogens(even though they
aren't
a living organism)
Protoctists are Eukaryotic organisms. Bacteria are prokaryotic organisms. Viruses are particles and smaller than bacteria
6) Enzymes
Enzymes are biological catalysts produced by living things, to increase the speed of a reaction without being changed or used up.
Enzymes reduce the need for high temperatures, and we
only
have enzymes to speed up the
useful chemical reactions
in the body. These reactions are called
metabolic reactions.
Enzymes are all
proteins
and they are made up of
chains
of
amino acids
, which are folded into unique shapes.
Enzymes are very specific and picky. They usually speed up only 1 reaction.
A
substate
is a molecule that is
changed
in a reaction. Every enzyme molecule has an active site -- the part where a substrate joins on to the enzyme. This is called the 'lock and key' model.
Enzymes like it warm but not too hot i.e. higher temperature increases the speed of the reaction up to a point. If it gets too hot then it changes the shape of the enzymes active site. So the substrate won't fit. This is called
denatured
Enzymes also need the right pH level. If the pH is too high or low, then it changes the shape of the active site and denatures the enzyme. Enzymes typically need a pH 7.
7) Diffusion
Diffusion is how a lot of substances get in and out of cells.
Particles move about randomly and then they end up evenly spaced
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration
Cell membranes hold the cell together but they let stuff in and out as well via diffuison,osmosis and active transport
Only small molecules can diffuse through cell membranes like glucose, amino acids, water and oxygen
8) Osmosis
Osmosis is a special case of diffusion. It is the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
A partially permeable membrane is just one with very small holes in it.
9) Active Transport
Active Transport is the movement of particles against a concentration gradient(i.e. from an area of lower concentration to an area of higher concentration) using energy released during respiration
Example 1:
Active transport is used in the digestive system when there is a low concentration of nutrients in the gut, but a higher concentration of nutrients in the blood.
Example 2:
Active transport is also used by plants — it’s how they get minerals from the soil(lower mineral concentration) into their root hair cells(higher mineral concentration)
2) Levels of organisation
A typical animal cell contains:
Nucleus, Cytoplasm, Cell membrane, Ribosome, Mitochondria.
A typical plant cell contains:
everything an animal cell contains plus vacuole, chloroplasts and cell wall
a) Vacuole contains cell sap (a solution of sugar and salt)
b) Chloroplasts contains chlorophyll, which is used in photosynthesis
c) Cell wall contain cellulose, which surrounds the cell membrane. It supports the cell and strengthens it
Cells contain organelles, which are tiny structures within cells. There are 2 kinds of cells:
a) Eukaryotic (Eu - Kar - yo - tic) - These cells are complex, and they include all animal and plant cells.
b) Prokaryotic(Pro-Kar-yo-tik) - These cells are smaller and simpler than eukaryotic cells.
Cells can be single cell
or
multicellular. They are specialized. and they group as under:
a) Organelle are structures within Cells
b) Similar cells are organized as tissues, to carry out a particular function
c) Tissues are organized as organs.
d) Organs are organized as organ systems
Tissues can contain multiple cells and Organs can contain multiple Tissues
10) Movement of Substances
There are four factors for movement of substances (diffusion, active transport, osmosis):
a) surface area to volume ratio
b) distance
c) temperature
d) concentration gradient
