Jessica Firkin
Global Science
EDCU12037
Biological Science – Expert Group Activity
Sexual Reproduction
Sexual reproduction occurs when two individuals produce an offspring. The offspring
with have genetic characteristic or shared DNA from both parents.
Sexual reproduction in a plant:
Sexual reproduction in plants involves main two processes – pollination and fertilization.
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Pollination is when the male gamete (pollen) contained in the anther of the stamen
(male part of the flower) is transferred to the stigma of the pistil (female part of the
flower). Cross-pollination occurs when the pollen from one plant is transferred to the
stigma of another plant.
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Fertilization occurs when pollen trapped by the
stigma germinates to produce a long tube which
travels down the style and enters the ovary. The
pollen in the long tube (containing the male
gamete) fuses with the female gamete in the
ovule (contained inside the ovary). The zygote
(fertilized cell) then matures in the ovary to
become a seed. The seed then grows to produce
a new plant.
The following image shows the lifecycle of a sexually reproductive plant:
Plant Reproduction:
http://www.youtube.com/watch?v=rq6uIU7NP34&feature=related
Jessica Firkin
Global Science
EDCU12037
Asexual Reproduction
Asexual reproduction does not require two individuals to reproduce. The offspring
are genetically identical to the parent. There are different types of asexual
reproduction at the organism level these can include budding, fragmentation and
parthenogenesis.
Budding refers to offspring that develop on the parent that then break away and become
independent.
Fragmentation refers to when part of the adult breaks up, that part can then mature and
become an adult. The cycle can then be repeated.
Parthenogenesis refers to when a female produces an egg that does not require fertilization
from a male to develop.
An example of asexual reproduction:
1. The hydra develops a "bud".
2. The bud develops a mouth and tentacles
3. When it is fully formed the daughter hydra detaches from its
parent.
4. The daughter hydra is now fully independent.
“Komodo dragons, hammerhead sharks, Brahminy blind snakes, water fleas, certain
types of bees, scorpions, wasps, and even some types of birds, among others, are
capable of reproducing asexually, if necessary”.
Female Komodo dragons (the largest lizard) can produce offspring by parthenogenesis
when no male is available for sexual reproduction. Their offspring are homozygous at every
locus including having identical sex chromosomes. Thus the females produce all males
because, unlike mammals, females are the heterogametic sex (ZW) while males are
homogametic (ZZ).
Interesting: http://www.reptilechannel.com/reptile-news/2010/11/17/new-asexual-species-oflizard-discovered.aspx
Asexual reproduction: http://www.youtube.com/watch?v=gQqap0tqBYY
Differences between sexual and asexual reproduction
Sexual
Two parents: male + female
Genetically different to parent
Advantages: offspring will be different from
parent, better at adapting
Disadvantages: slower process, less
population
Asexual
One parent: male or female
Genetically identical to parent
Advantages: quick, efficient if suited to the
environment, populate faster
Disadvantages: Slow to adapt if the
environment changes