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B3.4 Animal Behaviour & Plant Responses
Worksheet One
ANSWERS
Orientation Responses 1
1. Innate refers to a behaviour being inherited by an organism whereas a learnt
behaviour is acquired by the organism within its life.
2. Tropism is an orientation response where the organism grows towards or away
from a stimulus. Valid example used to illustrate response.
3. The organism moves towards the stimulus for a positive tropism and away from
the stimulus for a negative tropism.
4.
Tropism
Positive
phototropism
Negative
phototropism
Positive
geotropism
Negative
geotropism
Description
Organism grows
towards light
Organism grows
away from light
Organism grows
down towards the
pull of gravity
Organism grows
up away from the
pull of gravity
Organism grows
towards water
Positive
hydrotropism
Example
Survival
Advantage
Coleoptiles shoots Receives more
light for
photosynthesis so
has more energy
to grow faster.
Roots
Anchors plant in
ground and is able
to receive more
nutrients for
growth.
Roots
Anchors plant in
ground and is able
to receive more
nutrients for
growth.
Plant stems
Receives more
light for
photosynthesis so
has more energy
to grow faster.
Roots
Roots growing
towards soil that
is moister enables
then to receive
more water for
photosynthesis.
Positive
chemotropism
Negative
chemotropism
Positive
thigmotropism
Negative
thigmotropism
Organism grows
towards a
chemical
Organism grows
away from a
chemical
Organism grows
towards an object
they touch
Pollen tube grows
towards the
ovules
Plant roots grow
away from pipes
Increased
fertilisation.
Vines of climbing
plants e.g.
passionfruit
Organism grows
away from an
object they touch
Roots
Gains support
from structure so
can grow higher
faster to obtain
more light.
Grows in
direction in soil
where more
aerated to receive
oxygen for
photosynthesis.
Plant avoids
toxins.
5. Shoot
Annotated notes indicate:
 Directional light
 Auxin produced in the tip
 Auxin moves down the dark side of the shoot
 Auxin in high concentrations in the shoot initiate cell elongation
Root
Annotated notes indicate:
 Auxin produced in the tip
 Auxin moves down due to gravity
 Auxin in low concentrations in a root prevent cell elongation
6. Apical dominance is where the apical bud produces auxin in high concentrations.
This causes cells to elongate and grow faster at the apex. The auxin diffuses down
the plant and in high concentrations inhibits the growth in the lateral buds. When
the apical bud is removed the dormant lateral buds grow causing the plant to
branch outwards.
7. This response occurs to plants in the absence of light. The plant grows a long
weak stem, with the distance between internodes increased. Fewer, smaller leaves
that are pale yellow. The advantage is that the plant will grow to a light source
faster and will then be able to photosynthesise to produce energy to grow
normally.
8.
Abiotic
Non-living, chemical and physical factors in the
environment.
Adaptation
A feature of an organism that enables it to survive in its
habitat and reproduce.
Auxin
A plant hormone that promotes root formation and bud
growth.
Biotic
Living factors in the environment.
Chemo
Prefix for chemical .
Effectors
Organ at the end of a nerve, such as a muscle or gland
that responds to a stimulus.
Etiolation
Long, spindly and yellowing growth as a result of
insufficient light.
Geo-
Prefix for gravity.
Photo-
Prefix for light.
Receptor
Sense organ: an organ having nerve endings (e.g. in the
skin, eye, ear etc.) that respond to stimulation.
Stimulus
A detectable change in environment.
Tropisms
A growth response to a directional stimulus.