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Slide 1

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Reproductive strategies
Incomplete
Asexual and sexual metamorphosis
Resembles adult. Goes
Asexual through moults due to
Rapidly produces large number of genetically
hard outer exoskeleton
identical offspring ­"clones", for example binary
so have to shed to grow,
fission and budding. Bulbs (daffodils), runners
becomes vulnerable
(strawberries), tubers (potatoes)
+ Favourable characteristics Complete
+ Large numbers quickly metamorphosis
+ Only need one parent to reproduce Completely different to
- Can't adapt to environments adult. Larva hatches
Sexual and is specialised for
Two parents producing offspring, which are feeding and growth.
genetically different. Diploids produce haploids. Changes in pupa to
+ Genetic variety, can adapt to environment adult that's specialised
+ Development of resistant stage in life cycle, for dispersal and
withstand adverse conditions reproduction
+ Dispersal of offspring due to formation of spores
(fungi) seeds and larvae. Reduces intra-specific
competition External and internal fertilisation
- Less rapid (sexual)
External
Parental care Insects Fertilisation occurs outside the body, gametes
Reptiles leave eggs Fertilised internally. are discharged into water. In frogs the joining
before hatched. Embryo developed
of the egg and sperm is facilitated by sexual
Birds and mammals outside the body
(maggots).
coupling and amphibians return to water to
have more parental breed.
care. Laid on food source.
- Large wastage as many gametes are
The lower numbers of
produced to increase chance of fertilisation
offspring, the more
- Offspring are vulnerable
care, as not enough
time/energy to Internal
provide warmth, food Most terrestrial animal, fertilisation occurs
or shelter, and can outside body. Needs organ to introduce sperm
Mammals
also train offspring. Embryo retained in
to egg.
uterus/womb but no + Egg is enclosed in protective covering when
shell and nourished it leaves body in amniotic egg (birds and
Reptiles and birds from mother's blood
supply via placenta.
reptiles). In humans further development in
Amniotic egg, has fluid
filled cavity within shell Young born at amniotic fluid to derive further nourishment
membrane that encloses advanced stage (so run through placenta.
embryo in yolk sac. Birds from predators)
+ Young are born more developed
incubate eggs and embryo
develops outside body. + Less wastage
+ Gametes don't need water
+ Male gamete is more independent…read more

Slide 2

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Colonisation of the land by Angiosperms
Organism Confined to..
Algae Aquatic environment
Mosses/ferns Damp areas as males gametes
need film of water
Conifers/flowering plants The land becoming
independent of water
Flowering plants 300,000
Well suited to life on land species of
as they have efficient flowering
xylem, carrying water and plants, most
successful
to support. terrestrial
Pollen grains with hard plants
coat to avoid desiccation,
containing male gamete
which is transferred to Male gametes travel through
female part of plant. Male tissue of female part to egg via
gamete is dispersed by pollen tube. Sexual
wind (grasses) or insects. reproduction no longer
(colourful flowers) depends on gametes travelling
through film of water.
Why are flowering plants so successful?
1. Matter of weeks for seed to flower
2. Seed has food store for when leaves
haven't grown above ground to
photosynthesise
3. Humus produced, which recycles
nutrients from decayed leaves due to
leaves falling off.…read more

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