Inquiring About the World of Life
o Evolution is the process of change that has changed life on Earth from
the beginning to the variety of organisms today.
o Organisms living today have been modified from their common
o Emergent properties are due to the arrangement and interactions of
parts as complexity increases.
o Eg. When a severe brain injury occurs, even though all the brain parts
are present, the brain may not function like before.
o Our thoughts and memories are emergent properties of a complex
network of nerve cells.
The Power and Limitations of Reductionism
o Breaking apart an organism disables it from functioning, however we
are unable to understand an organism or cell if we don’t take it apart.
o Reductionism is reducing complex systems to simpler components so
that it is easier to study.
o A system is the combination of components that function together.
o Systems Biology is to construct a model for the dynamic behaviour of
whole biological systems. The right model allows scientists to predict
how a change in one or more variable can affect the component or
the entire system.
o The ecosystem involves two processes.
o The first is the cycling of nutrients.
o The second is the one-way flow of energy from sunlight to producers to
o Producers are plants that use light energy to make sugar.
o Consumers are animals that eat the producers and other consumers. Energy conversion
o The exchange of energy between an organism and its surroundings
requires a form of energy converting into another.
o A plant absorbs light energy and converts it to chemical energy stored
in sugar molecules.
o Animal’s muscle cells uses sugar for power movements, they convert
chemical energy to kinetic energy.
o In all these energy conversions, some of the energy is converted to
thermal energy which gives off heat to the surrounding.
o Cells are an organism’s basic units of structure and function.
o The division of cells to form new cells is for reproduction, growth and
repair of multicellular organisms.
o All cells share certain characteristics.
o Every cell is surrounded by a membrane that controls the passage of
materials between the cell and its surroundings.
o Every cell uses DNA as its genetic information.
o Microorganisms such as Bacteria and Archaea are prokaryotic cells.
o Plants and animals are Eukaryotic cells.
o An eukaryotic cell is split by internal membranes into different
o The nucleus is the largest organelle in most eukaryotic cells.
o The other organelles are located in the cytoplasm which is the place
between the nucleus and outer membrane of the cell.
o Prokaryotic cells are smaller and simpler compared to eukaryotic cells.
o The DNA is not separated from the rest of the cell by being surrounded
in a membrane-bounded nucleus.
o DNA – deoxyribose nucleic acid
o DNA is the substance of genes which is transferred from parents to
o Chromosomes have most of the cell’s genetic material, it’s DNA.
o Each chromosome has one long DNA molecule with lots of genes
arranged along its length.
o The DNA of chromosomes replicates as a cell begins to divide, and
each of the two cellular offspring inherits a complete set of genes.
o The molecular structure of DNA enables it to store information. o Each DNA molecule is made up of two long chains arranged in a
o Nucleotide is the block of molecules that form building blocks of
DNA/RNA when linked together.
o DNA of genes controls protein production indirectly and uses RNA as a
intermediary (acting between).
o The sequence along a gene makes a copy (transcribe) into RNA which
is then changed (translate) into a specific protein with a unique shape
o A genome is the entire information of genetic instructions that an
o Five kingdoms:
- Single-celled eukaryotic organisms
o Domain bacteria and domain Archaea are prokaryotic cells.
o Prokaryotic cells are single-celled and microscopic.
o Plants make their own sugars and other foods by photosynthesis.
o Fungi are decomposers – they break down dead organisms and
organic wastes and get their nutrients from these.
o Animals get food by eating and digesting other organisms.
Charles Darwin and the Theory of Natural Selection
o Darwin said that existing species arose from a succession (thing after
another in order) of ancestors – descent with modification
o His second point was to suggest a mechanism (structure) for descent
with modification – evolutionary mechanism natural selection.
o Individuals in a population can have different traits which is able to be
passed on from the parents to the offspring.
o A population can produce more offspring than can produce offspring
on their own. Viruses
o Injecting a virus’s DNA into a cell enables the virus to take over the
bacterium and produce many new viruses.
o Viruses cannot reproduce or carry out metabolic activities outside the
o A virus consists of a nucleic acid surrounded by a protein coat.
o A virus’s genome consists of double-stranded DNA, single-stranded
DNA, double-stranded RNA single-stranded RNA, depending on the
type of virus.
o A virus is called DNA virus or RNA virus depending on the nucleic acid
that makes up its genome.
Capsids and Envelopes
o A capsid is the protein shell that surrounds the viral genome.
o A capsid can be rod-shaped, polyhedral or a more complex shape,
depending on the type of virus.
o Capsomeres are the protein subunits that make up capsids.
o Some viruses have different structures that help them infect the host
o Eg. A membranous envelope surrounds the capsids of influenza viruses
and many other viruses found in animals.
o The viral envelopes obtained from the membranes of the host cell
contain host cell phospholipids and membrane proteins. They also
contain proteins and glycoproteins of viral origin.
o Bacteriophages are the viruses that infect bacteria. Their capsids have
heads that surrounds DNA. Attached to the head is a protein tail with
fibres where the bacteriophages attach to a bacterium.
Reproduction of viruses
o Viruses only reproduce in host cells.
o Viruses lack metabolic enzymes and equipment for the making of
o Each type of virus can infect cells of a limited variety of host