lecture 6- the origin of species Flashcards
What does polymorphic mean?
Occurs in several different forms
What is the polymorphic shell colours for Cepaea Nemoralis
Brown, pink, yellow
What determines shell colour in Cepaea Nemoralis?
three alleles
the main predator of Cepaea Nemoralis
Turdus Philomelos (Thrush)
whats a thrush anvil?
the stone that thrush birds use to break opem Cepaea Nemoralis shells
when is the population of yellow shelled Cepaea normalis highest? why?
the percentage of yellow shelled cepaea normalist is higher than the general population in April, as they blend in better at the avaliable background(green) and are less predated by thrush birds
what is macroevolution
evolutionary changes over long periods of time on a large time scale (eg. mass extinction, adaptive radiation)
what is micro evolution
changes within populations, at or below the species level. this is the basis for natural selection
is macro or micro evolution the basis for natural selection? why?
micro evolution, as its the adaptation of species to thier environment
explain the difference between a genotype and a phenotype
the genotype is the genetic makeup of an organism which consists of heritable genes
the phenotype is the genotype combined with the environment, and is the observable traits of an organism
what is a homozygous chromosome?
when an individual inherits the same allele of a gene from each parent
what is a heterozygous chromosome?
when an individual inherits different alleles of a particular gene from each parent.
what are homologous chromosomes?
these are two pieces of dna within a diploid organism.one is inherited from the mother, one from the father
what is karyotyping?
the process of organising all the chromosomes within an organism, thus providing a genome wide snapshot
what is asexual reproduction?
do the number of chromosomes change?
a form of evolution that does not involve the fusion of gametes. the number of chromosomes does not change
what does asexual reproduction occur via?
mitosis
how does mitosis occur? which form of reproduction does it relate to?
asexual reproduction.
one cell divides twice to form two daughter cells, they have the same number and type of chromosomes as the parents.this is diploid cell dividing.
what form of reproduction creates clones
asexual
what are the four methods of asexual reproduction?
1.budding
parthenogenesis
3.binary fission
4.vegetative reproduction and budding
explain how asexual reproduction occurs via binary fission
the organism replicates it’s dna, then divides into two parts via Cytokenisis. two cells of the same size are created, each having a copy of dna
what is the division process in binary fission
cytokinesis
what form of organism is budding common in?
unicellular organisms such as bacteria of yeast
how does budding occur?
A new cell cell grows as a bubble on the side of a parent cell. it increases in size and then eventually splits. it has the same genetic material
are the daughter cell and parent cell the same size in budding?
the daughter cell is significantly smaller in size
what is parthenogenesis?
this is when reproduction occurs on an egg WITHOUT fertilisation from a male. This means there is only genetic input from one parent
in what two ways can parthenogenesis occur?
obligatley or faculatively
explain the difference between obligate and faculative parthenogenisis
obligatley= when its the "usual" mode of reproduction and must occur in some species faculatively= a needs must approach
explain the two ways of vegetative reproduction. give an example
this occurs when a new plat growth forms from a SPECIALISED REPRODUCTIVE STRUCTURE and an exact clone is created. strawberry runners
or, occurs when a new organism grows from the fragment of another.eg.cutting a worm in half
what is the difference between sexual and a sexual reproduction?
sexual reproduction involves the fusion of gametes, a sexual reproduction does not
what is the difference between a diploid and a haploid?
A diploid has two chromosomes, one from each parent. a haploid has one set
how many daughter cells does meiosis produce?
this process produces four daughter cells, each with half the number of chromosomes as the parent cells
why does meiosis drive genetic variation?
unlike in a sexual reproduction, the offspring are not genetically identical to the parents
how is genetic difference in meiosis driven (three mechanisms)
- the independent assortment of chromosomes
- the crossover of dna between homologous pairs causes genetic exchange in meiosis
- random fertilisation.
how does random fertilisation lead to genetic difference?
gametes contain many different alleles. when forming a zygote, all this genetic material can create up to 8 million different combinations. This causes great amounts of variation to be possible.
what are the four chromosomal mutations?
- deletion
- duplication
- inversion
- reciprocal translocation
what is an snp?
single point mutations. they are single point nucleotide changes that are markers for genetic diversity.
what is polyploidy?
when organisms have more than two sets of chromosomes
what results in polyploidy?
faults in cell division or environmental effects
why does polyploidy most often result in offspring being sterile?
the chromosomes cannot pair up effectively during meiosis, meaning gametes cant be produced
what are the two forms of polyploidy?
- autopolyploidy
2. allopolyploidy
which form of polyploidy results from genome duplication within the same species?
auto polypolidy
how does autopolyploidy occur?
errors in mitosis or meiosis. the ggenome duplication comes from two members of the same parent species, and the cells a tetraploids
where do the chromosomes originate from in allopolyploidy?
two different related species that have interbreed and hybridised
which form of polyploidy results from hybridisation?
allopolyploidy
what can result in reproductive isolation?
Polyploidy, as offspring are almost always sterile
at what level does molecular variation occur?
dna,rna and protein level
what is silent/non coding dna subject to?
Genetic drift or mutation. NOT NATURAL SELECTION
how can silent dna cause evolution?
it impacts the phenotype, which in turn undergoes selection
