Everything you'll need for the OCR AS-Level Biology B (Advancing Biology exams):
-Core concepts
-Methodology for practicals
-Equations and formulas
-Key words
-Diagrams
-Graphs
Five Kingdoms:
o Fungi
o Plantae
o Animalia
o Protoctista
o Prokaryotae
Prokaryotae:
o Organisms which do not have a membrane bound nucleus
o MOST reproduce via BINARY FISSION – cells grow, DNA
replicates and cell divides into two
Fungi:
o All are HETEROTROPHIC – complex organic molecules are
broken down to simpler ones
o Cell walls are made of – CHITIN
o Store CARBOHYDRATE in the form of – GLYCOGEN
o Show LITTLE TISSUE DIFFERENTIATION which means there
are no distinct organs
o EXTRACELLULAR DIGESTION – HYPHAE
Plantae:
o All are AUTOTROPHIC – simple inorganic molecules are used
to make more complex organic molecules
o Sub-divided into two main groups:
NON-FLOWERING e.g. MOSSES and ferns
FLOWERING e.g. trees, grasses, blue bells
o Cell walls are made of – CELLULOSE
o Show TISSUE DIFFERENTIATION into roots, stem and leaves
o Contain CHLOROPHYLL
o Store CARBOHYDRATE in the form of STARCH
Animalia:
o All are HETEROTROPHIC – complex organic molecules are
broken down to simpler ones
o Multicellular, don’t have CELL WALLS
o Contain specialised cells and tissues e.g. NERVOUS and
MUSCLE TISSUES
o TISSUE – collection of similar cells with a common function
o Store CARBOHYDRATE in the form of – GLYCOGEN
,Biology Revision:
Homeostasis:
Homeostasis – maintaining internal conditions within narrow limits
Usually involves – negative feedback,
Effectors – are either muscles or glands, they bring about response
to a stimulus
Receptors – detect stimuli e.g. thermo receptors
Negative Feedback – departure from a set level is detected by
receptors. These send information to effectors which bring about a
return to the original value.
Thermo regulation - the regulation of body temperature
Endothermic animals – warm blooded e.g. mammals, birds. These
produce lots of heat and retain what is required
Exothermic animals – cold blooded e.g. reptiles, fish, and
amphibians. These produce less heat and retain very little of it.
Short-term heat production – (1) shivering – rapid contraction and
relaxation of muscle fibres. Major disadvantage – uses lots of
energy (2) release of hormone adrenaline – from adrenal glands,
this raises the metabolic rate of the individual.
Basal Metabolic Rate – energy expended by a resting fasting person
in a room at a comfortable temperate.
Factors that effect metabolic rate:
Age
Sex
Diet
Activity
Health
Drugs
Long-term heat production – increased production of the hormone
thyroxine from the thyroid gland in the neck.
Heat loss:
Radiation – loss of heat via electromagnetic waves
when body is warmer than the surroundings.
Evaporation – mainly via sweating
Conduction – the loss of heat through contact with an
object/medium that is cooler than the body
Regulation of heat loss:
Vasoconstriction and vasodilatation – alter blood flow
to the skin and hence regulate heat loss by changing
the diameter of the arterioles in the skin
Vasodilatation – widening of arterioles, increase blood
flow
Vasoconstriction – narrowing of arterioles decrease
blood flow
Erector pili muscle – reduce heat loss the muscles contract causing
hair to stand upright. This traps a still layer of air close to the skin
and reduces heat loss.
Adipose tissue – fat storage tissue
Hot and cold thermo-receptors in the skin send nerve impulses to
the hypothalamus which brings about the changes necessary to
restore the correct temperature.
, How natural selection may lead to speciation:
Species – Organisms that reproduce to produce FERTILE offspring
Population – Group of organisms of the same species found in the
same place (habitat) at the same time
Mechanisms which may lead to speciation:
o Isolation:
Physical isolation – continental drift, deforestation,
mountain range, volcanic activity, floods. Road building
Reproductive isolation – sexual selection, reproducing at
different times of year
o Natural Selection:
Some genetic variation between separated groups
RANDOM mutations occur within each group leading to
further genetic variation between groups
ENVIROMENTAL CONDITIONS faced by each group
DIFFER, the SELECTION PRESSURES on each group also
DIFFER
The individuals in the two groups may start to occupy
different NICHES
Over an EXTENDED period of time, through MANY
generations, there will be different CHANGES IN the
ALLELE and phenotype FREQUENCIES in the separated
groups
o Speciation:
Eventually the genetic/phenotypic differences between
members of the separated groups becomes so great that
they CANNOT INTERBREED TO PRODUCE FERTILE
OFFSPRING, this means a new species has been produced
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