U2 definitions Flashcards
arthropods
joint-legged invertebrate that are identified by their segmented body, typically with pared appendages eg fruit fly,. wasps
sodium-potassium ATPase?
the enzyme that acts as the sodium-potassium pump bringing three sodium ions into the cell and taking two potassium ions out of the cell during the cycle of action.
chordates
sea squirts and vertebrates eg birds, mammals, reptiles, amphibians, fish
nematodes
also called roundworms
unsegmented thread-like body
many are parasitic living inside their hosts eg.flukes and tapeworm
why are carriers less likely to be affected by deleterious mutations on one of their X chromosomes?
because of random X chromosome inactivation
what does the SRY gene on the Y chromosome do?
encodes testes- determining factor (TDF) and determines the development of male characteristics.
what can sex be determined by?
- sex chromosomes (In most mammals)
- environmental temperature of egg incubation (in some reptiles ie. Mississippi aligators)
- size
- competition
- parasitic infection
- resource avaliability
why do the benefits of sexual reproduction outweigh the costs?
due to an increase in genetic variation in the populations
parthenogenesis
reproduction from a female gamete without fertilisation
more common in colder environments which are disadvantageous to parasites, or regions of low parasite density or diversity
example of horizontal gene transfer
plasmids between bacteria and yeasts
why may co-evolutionary interactions between parasites and host select for sexually reproducing hosts?
- hosts better able to resist and tolerate parasitism have greater fitness.
- if hosts reproduce sexually, the genetic variability of the offspring reduces the chances that all will be susceptible to infection by parasites.
- the genetic variation in their offspring increases the chances that some of the offspring will have improved ability to exploit their hosts.
why may co-evolutionary interactions between parasites and hosts select for sexually reproducing hosts?
hosts better able to resist and tolerate parasitism have greater fitness
using external fertilisation
allows very large numbers of offspring to be produced
many gametes are predated and not fertilised
there’s little to no parental care
few offspring survive
using internal fertilisation
increases the chances of successful fertilisation
fewer eggs needed
retained internally for protection and or development
higher offspring survival rate
the disadvantage of internal fertilisation
energy is required to find a mate and required the difficult direct transfer of gametes from one partner to another
independent assortment
the order in which chromosomes line up at the equator of the cell during meiosis I. This is random and irrespective of their paternal origin.
biotic selection pressures
competition
predation
disease
parasitism
abiotic selection pressures
temperatures pH light intensity salinity ALL SELECTION PRESSURES INCREASE THE RATE OF EVOLUTION
conditions for HW
no mutation no gene flow no natural selection large population size RANDOM MATING
fitness is an indication of?
a measure of?
refers to?
- an indication of an individual’s ability to be successful at surviving and reproducing.
- a measure of the tendency of some organisms to produce more surviving offspring than competing members of the same species
- the contribution made to the gene pool of the next generation by individual genotypes
commensalism
is a symbiotic relationship in which only one of the species substantially benefits and the other is neutral
if the absolute fitness is 1?
if greater than 1?
less than 1?
then the frequency of that genotype is stable
an increase in genotype frequency
a decrease in the frequency of genotype
what is classic taxonomy based on?
morphology