heredity - reproduction Flashcards
How does reproduction ensure the continuity of a species?
without reproduction, new individuals are not produced → species will go extinct
in stable environments, asexual reproduction is advantageous → large numbers of offspring + minimal energy used
sexual reproduction → variation → increases the likelihood of a species surviving environmental changes (favourable traits)
agricultural practices → potential to negatively influence the genetic of a species
advantages of external fertilisation
little energy required
large number of offspring
offspring spread more widely → less competition
disadvantages of external fertilisation
gametes go unfertilised
offspring less protected
offspring die from environment
advantages of internal fertilisation
more likely to occur
embryo protected from predators
more likely to survive
disadvantages of internal fertilisation
high energy
less offspring
more energy to raise offspring
plant fertilisation
The process of the male gamete (pollen) uniting with the female gamete (ovum)
pollination
Transfer of gametes from one plant to another
pollinating agents
wind or animals (bees) - agents that help pollen spread from one plant to another
self pollination
Pollination of the one flower by its own pollen. These are less genetically diverse.
cross pollination
rely on outside agents for transfer of pollen from one plant to another.
asexual advantages and disadvantages
efficient/fast
short time required to reproduce
no variation → increase risk of disease
hyphae
tiny thread of cytoplasm surrounded by a plasma membrane → covered by a wall of chitin
mycelium
feeding structure of a fungus → below ground
HOMOthallic
self-fertile → ability of a single spore to produce sexually reproducing colony
HETEROthallic
Requires haploid cells to fuse in order to produce new individuals.
binary fission
cell elongates → genome replicates (any plasmids replicate) → DNA separates to either side → cleavage furrow → two identical daughter cells
conjugation
direct transfer of DNA from one bacterial cell to another → introduce genetic variation
transformation
when naked DNA is taken up from the environment by bacterial cells
transduction
the use of bacteriophage (bacterial virus) to transfer DNA between cells
types of sexual reproduction in protists
syngamy → complete fusion of gametes → diploid zygotes
conjugation → temporary union to exchange haploid → forms zygote nucleus → each individual produces daughter cells by binary fission
zygote
diploid cell resulting from the fusion of gametes
blastocyst
cell differentiation of cells has occurred. Inner cell mass (ICM) will form the embryo.
The outer layer (called trophoblast) will form the placenta
implantation
the attachment of the blastocyst to the wall of the uterus
morula
early stage of cell division - no differentiation
process of animal fertilisation
- sperm makes contact with egg → burrows through corona radiata
- sperm attaches to receptor of zona pellucida
- digestive enzymes released from acrosome, sperm burrows through zona pellucida
- plasma membranes of sperm and egg fuse
- sperm nucleus enters egg
Follicle stimulating hormone
Causes the release of an egg from an ova into the fallopian tube.
Luteinising Hormone
Develops the ovum and causes ovulation and stimulates production of estrogen and progesterone
Estrogen
promotes the menstrual cycle but decreases after ovulation
Progesterone
prepares the uterus for implantation and maintains the uterus during pregnancy.
Prevents the release of further eggs
Decrease in levels of progesterone occur if fertilisation does not occur causing breakdown of the uterus wall.
androgen
Hormones involved in male sex organs and the production of male gametes.
estriol (weak estrogen)
inhibit further product of progesterone - preventing uterine contractions
increasing smooth muscle cells of the uterus
role in birth oxytocin (love hormone)
stimulates the uterine muscles to contract the birthing process
releases milk during breastfeeding
prolactin
mothering hormone
peaks at labour
central to milk production
artificial pollination advantages and disadvantages
create plants with desirable traits
breed new variety of plants
cannot guarantee favourable trait is passed on
reduced genetic variation
artificial insemination advantages and disadvantages
large number of females inseminated
semen is easier to transport than a whole animal
cannot guarantee favourable trait is passed on
reduced genetic variation
selective breeding
The intentional mating of individuals with desirable traits, in the hope that offspring will express those same traits in their phenotype.
cloning
genetically identical copies of an organism are made without using the process of sexual reproduction.
cloning advantages and disadvantages
cloned plants have identical requirements to grow
guaranteed to express desired trait
identical offspring → disease susceptibility
expensive with limited advantages
ethical worries → cloning of humans
transgenesis
process by which a gene is removed from one species and inserted into the genome of another species.
transgenesis advantages
guaranteed to express desired traits
increased yield and nutritional value
reduced chemicals needed
transgenesis disadvantages
identical offspring
espace of GMO population into wild
trade issues with anti-GMO countries
long term effect on health unknown
