exam 3 Flashcards
how many pairs of chromosomes are there
23 pairs
what is a genotype
our DNA
what is the difference between a heterozygous genotype and a homozygous genotype
heterozygous genotype: copies are different alleles
homozygous genotype: both copies are the same allele
what is a phenotype
our observable characteristics or traits
what affects your phenotype
our genes, environment, and chance define your phenotype
what does it mean to say a trait is dominant or recessive
dominant- shown when a person only has one copy of that gene
recessive- when two copies of that gene is present
what are the genotype and phenotype of someone who is a carrier
the trait is only shown on the recessive gene
ex: Aa
what is incomplete dominance
phenotype of the heterozygote is intermediate between the two homozygotes Cs = wavy hair (CC =curly and ss = straight)
how does meiosis halve the number of chromosomes per cell
lines them up along the midline and then pulls them apart into two separate cells
what is the difference between autosomes and sex chromosomes
22 pairs of autosomes and 1 pair of sex chromosomes
male genotype
X Y
what is the location and function of the SRY gene
located on the Y chromosome, has instructions for making,ing a regular protein, signals for gonads to develop into testes
what is a sex-linked trait
located on either the X or Y chromosome
how can you use a Punnet square to predict the probabilities of X-linked phenotypes for children given the genotypes of the parents
you can match the two genotypes of each parent to make a percentage of their chances to get certain traits
what are the symbols used in pedigrees
X Y
why is a genotype not necessarily sufficient to predict phenotype
because phenotype is based on genes environment and chance
what error in meiosis can change the number of chromosomes in a cell
the failure of chromosomes to separate during meiosis
how does the number of chromosomes in a cell relate to Down syndrome
they have extra or less chromosomes
what is a gene pool
collection of all of the alleles in a population
what is a population
a group of organisms in a geographic area
what is genetic drift
random changes in the allele frequencies of a population between generations
what are two major mechanisms of genetic drift
the founder effect, the bottleneck effect
how does natural selection result in adaptation
differential survival and reproduction of individuals within a population in response to environmental pressure
what is necessary for natural selection to occur
individuals within a population vary, some variants have more offspring
what is fitness and how does it relate to natural selection
organisms ability to survive and reproduce in a particular environment, higher fitness = increased likelihood of alleles being passed to the next generation
female genotype
X X
when did life first appear on earth and what type of life was it
first were prokaryotes 3.7 by a
what is the order of events for the history of life on Earth
3.7 bya = first prokaryotes
2.7 bya= oxygen accumulates
2.1 bya = eukaryotes
1.5 bya= multicellular eukaryotes
1.0 bya= ancestors of land plants
540 mya= Cambrian explosion (aquatic) and appearance of animals
500 mya = first true plants and colonization of land
what are phylogenetic trees
visual representations of evolutionary history among organisms - show ancestor - desendant relationships
what is a species
groups of actually or potentially interbreeding members that produce viable fertile offspring
what is the Biological Species Concept
species united by being reproductively compatible
gene flow: holds populations together genetically
what are the three largest classifications of life
Archaea, Bacteria, and eukarya
what are the four main groups of euaryotes
fungi, protists, animals, plants
briefly characterize: plants
multicellular autotrophs
internal digestion
cell walls- cellulose
food source for humans
briefly characterize: animals
heterotrophs
internal digestion
no cell walls
multicellular
briefly characterize: protists
autotrophs and heterotrophs
external and internal digestion
cell walls and no cell walls
mainly unicellular some multicellular
briefly characterize: fungi
mainly multicellular
heterotrophs
cell walls- chitin
external digestion
why is their so much biodiversity
environments are constantly changing
random mechanisms of evolution
natural selection and adaptation
