BIOL1008 Study Guide - Midterm Guide: Pineal Gland, Glycoprotein, Spermicide
Reproduction
Asexual Reproduction
Sex is not necessary for reproduction
Asexual reproduction undergoes cell division through fission, budding or
regeneration
Fission: separation of a parent into two (binary) or more individuals of about equal
size e.g. staphylococcus aureus (prokaryote), sea anemone (multicellular organism)
Budding: cellular division or ‘pinching’ of small ‘bud cells’ off a parent cell- new
individuals arise from outgrowths of existing ones e.g. hydra sp.
Amoeba reproduces through mitosis (single-celled eukaryote)
Parthenogenesis
Form of reproduction in which the egg develops into a new individual without
fertilisation
Many species of bees and wasps
oFertilised eggs= female (2n)
oUnfertilised eggs= male (1n)
E.g. Komodo dragons- Sungai gave birth to some males without any contact with
other male komodo dragons, Flora never had any contact with males but produced
offspring
Somatic cells vs. gametes in humans
Somatic cells Gametes
- Growth and maintenance cells
- Diploid (2n)- two copies of each
chromosome
- Identical to parent cell (as long as
no mutations)
- Produced via cell division of mitosis
- Sex cells
- Haploid (1n)- one copy of each
chromosome
- Non-identical
- Produced via cell division of meiosis
Sexual Reproduction
Reproduction that brings the
genes of two parent
individuals together,
generating a new individual (forms
and grows from the zygote)
Always involves meiosis whereas asexual
reproduction occurs in many ways
Meiosis fertilisation
Fertilisation: fusion of haploid (1n) gametes to form a diploid (2n) zygote
Male gamete= sperm (smaller than egg and independently motile)
Female gamete= ovum/ egg/ oocyte (larger than sperm)
Germ cells= cells that produce gametes
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External fertilisation
Depends on availability of moisture (sperm are motile, need to swim otherwise will
dry out)
Synchrony requires (to have a greater chance of survival due to same timing with
sperm and eggs)
Probability of fertilisation is low (so produce lots of sperm)
Without parental care, the odds of subsequent survival can also be low
Can include parental care
Doesn’t necessarily mean lack of physical contact
Internal fertilisation
Dry environment (may have evolved because we had to cope with dry environments
on land)
Synchrony required
Probability or fertilisation and survival is higher than external
Requires physical contact
Advantages of sex
Produces offspring with more variation- different to parents and siblings
Recombination can get rid of harmful mutations
Facilitates response to environmental change
Allows genome of species to carry significantly more information that genome of an
individual
Encourages collaborations (investment)
Asexually producing species often thrive for a time, but are slower to adapt to
change
Some organisms that usually reproduce asexually can reproduce secularly but only
do so in times of stress of uncertainty in the environment
Disadvantages of sex
Courtship and mating involves risks for parents
At low population densities sexual reproduction may be difficult to coordinate-
compares with asexual reproduction which ensures that reproduction will be
possible at any time
Two-fold cost of sex
oIn human sexual reproduction females contribute the resources to foetus but
only half the genes and males contribute half the genes but no resources
oBeneficial for an individual to pass on as many genes as possible- measure of
fitness
oAn asexual female would be able to transmit twice as many genes for the
same ‘price’ per offspring
Recombination scrambles genotypes and can disrupt favourably adapted gene
combinations
Meiosis, fertilisation, and finding a mate take longer than mitosis, slowing the pace
of reproduction
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Gender Determination
Gender assignment
Chromosomal makeup- XX or XY
Internal organs- testes or ovaries
External genitalia- penis or vagina
Gender assignment needs to take into account all three aspects
Chromosomal Makeup
Packing of genes
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Asexual reproduction undergoes cell division through fission, budding or regeneration. Fission: separation of a parent into two (binary) or more individuals of about equal size e. g. staphylococcus aureus (prokaryote), sea anemone (multicellular organism) Budding: cellular division or pinching" of small bud cells" off a parent cell- new individuals arise from outgrowths of existing ones e. g. hydra sp. Form of reproduction in which the egg develops into a new individual without fertilisation. Many species of bees and wasps: fertilised eggs= female (2n, unfertilised eggs= male (1n) Komodo dragons- sungai gave birth to some males without any contact with other male komodo dragons, flora never had any contact with males but produced offspring. Diploid (2n)- two copies of each chromosome. Identical to parent cell (as long as no mutations) Haploid (1n)- one copy of each chromosome. Reproduction genes of two individuals generating a new and grows from. Always involves meiosis reproduction occurs in many ways.
