bio dec3 Flashcards
(126 cards)
1
Q
why can the spleen be considered a large lymph node?
A
because it contains white pulp filled with B and T lymphocytes that are responsible for humoral and cell-mediated immunity.
2
Q
Hardy-Weinberg equation
A
p2+2pq+q2=1 and q+p=1; q=frequency of recessive allele,
p=frequency of dominant allele.
to find heterozygote allele type: 2pq
3
Q
erythropoietin
A
hormone that increases red blood cell mass at high altitude (low O2). body’s compensation for low O2 loss
4
Q
where is unconscious movement coordinated
A
the cerebellum
5
Q
disruptive selection
A
shifting in allele frequencies of population to either extreme.
6
Q
when do sperm start to be produced
A
at puberty
7
Q
gametes possible
A
2^n where n is the number of heterozygous pairs
8
Q
cells of the stomach
A
parietal cells - produce HCl. chief cells - produce pepsinogen that’s activated to pepsin by HCl. pepsin digests proteins. G cells - make gastrin, hormone that stimulate acid secretion in parietal cells mucosal cells - make mucus that lines stomach.
9
Q
absorption in small intestine
A
bile helps out, villi and microvilli provide increased surface area for absorption . all nutrients go to the liver first and then go into blood circulation. SI absorbs amino acids, hydrolyzed fats, water, monosaccharides, and vitamins.
10
Q
how are fats absorbed by the body
A
absorbed by lymphatic system. transport fats to thoracic duct.
11
Q
lymphatic system
A
collect excess interstitial fluid (lymph) and carry it back to the circulatory system.
12
Q
How is lymph moved
A
mainly by the pressure of skeletal muscles - act against lymph vessels, and move the liquid forward. The liquid inside the lymph vessel is at a very low pressure and because of the pressure difference, liquids from the tissues are drawn into the lymph system. returned to the blood via lymph vessels that drain into the large veins of the cardiovascular system.
13
Q
lacteals
A
collect fats from small intestine and transport them to the circulatory system.
14
Q
where does lymphatic system join circulatory system
A
at the thoracic duct.
15
Q
lymph nodes
A
contain leukocytes which help filter the lymph and remove foreign particles. cleanses/filters extracellular fluids.
16
Q
respiratory system progression
A
nose/mouth, pharynx, larynx, trachea, lungs, bronchus, bronchiole, alveolar ducts, alveolar sacs, alveoli
17
Q
surfactant on alveolus
A
reduces surface tension along alveoli and facilitates gas diffusion across membrane. also prevents alveolar collapse
18
Q
partial pressure of gases in alveoli
A
- greater in the alveoli than in the blood so the net diffusion of oxygen is from alveoli to capillaries where RBCs can become oxygenated.
- partial pressure of CO2 is greater in the blood than in the alveoli and the net diffusion of CO2 is from the capillaries to the alveoli → then can be eliminated from the lungs through exhalation.
19
Q
functions of the nose and mucus
A
detect odors, warm and humidify inhaled air, filter particulate matter.
nasal passage, bronchioles, and resp. passageway is lined with mucus that keeps passages moist and traps any particulate matter. cilia of epithelial cells move mucus towards pharynx for expulsion via coughing or swallowing.
20
Q
membranes around lung
A
surrounded by visceral (adjacent to lung) and parietal (outer) pleura with interpleural space in between. pressure differential between interpleural space and lungs keeps lungs inflated.
21
Q
inhalation and exhalation - movement of muscles
A
inhalation: diaphragm contracts, external intercostal muscles contract moving rib cage up and out. air enters lungs as a result of the vacuum that is created in them.
exhalation: diaphragm relaxes, external intercostal muscles relax, chest cavity size decreases.
22
Q
respiratory centers
A
cluster of neurons in medulla oblongata that regulate ventilation. their rhythmic discharges stimulate contractions in the diaphragm and the intercostal muscles.
23
Q
chemoreceptors
A
can modify neural signals for respiration. some found in aorta (aortic bodies) and carotid artery (carotid bodies) that connect to the medulla. carotid bodies respond to changes in pH and partial pressure of CO2 in blood. When a drop in pH is detected, rate and depth of ventillation are increased.
24
Q
change in pH of blood with CO2,
A
as CO2 in blood increases, pH drops because CO2 reacts with water to form carbonic acid which lowers pH.
25
where does transcription and translation happen?
transcription happens in nucleus and product leaves through nuclear pores
translation happens in cytoplasm
26
possible mutations in DNA
**base substitutions:** one base pair substituted for another transition - substitution of purimidine for another pyrimidine or purine for another purine.
**transversion:** subs. of a pyrimidine by a purine or vice versa
**deletions**: one or more nucleotides are lost from a sequence insertions: one or more nucleotides added to a sequence. may also be inserted at an incorrect location
27
repairs in DNA
**direct:** reverses damage without cutting phosphate backbone - ex. removing methyl group to restore original base.
**base excision repair**: when incorrect bases are in DNA. damaged base is recognized by glycosylase and hydrolytically removed from phosphate backbone. correct base is inserted and sealed by ligase. mismatch repair: fixes incorrect pairings
**nucleotide excision repair**: removes thymine dimers and bulky adducts. area of DNA surrounding and including damaged portion is unwound and endonuclease makes cuts on both 5’ and 3’ sides of the damage. base are removed by an exonuclease and DNA resynthesized using sister strand as template. ligase seals it up.
**post-replication repair:** used to repair double strand breaks. recombinational repair where single strand of DNA from a homologous chromosome is used to resynthesize the missing portion. broken ends can be rejoined directly and ligated together. original sequence is not always maintained and mutations such as translocations can often occur as a result.
28
thymine dimers
caused by UV radiation. nucleotide excision repair mechanism removes them.
29
Holliday model for recombination
explanation of events that occur during recombination. homologous pairs line up endonuclease nicks a single strand on each homolog at the same place. homologs exchange strands and are ligated together forming the Holliday structure. branch migration can occur, incorporation a portion of the opposite strand into each
molecule cleavage occurs: if same strands are cleaved, original chromosomes are reformed, if opposite strands are cleaved, recombinant chromosomes formed.
30
numerical abnormalities
**aneuploidy** - one or more chromosomes are missing or are present in more than the normal number. usually from nondisjunction.
**euploidy** - extra complete set of chromosomes are present or missing.
**mixoploidy** - mosaicism - 2+ genetically different cell lines within a single individual derived from a single zygote.
**chimerism** - 2+ genetically different cell lines within a single individual derived from different zygotes.
31
structural abnormalities
occur when part of chromo is duplicated, deleted, or switched to another part of the chromosome. chromosomal number is normal, but there is an excess or deficiency in genetic material can happen from recombination malfunction or misrepair of chromosome breaks.
32
autosomal monosomy
always lethal.
33
mitochondrial DNA
double stranded and short portion of triple stranded, circular DNA. has 37 genes - 24 code for RNA, 13 code for polypeptides which are used in the respiratory complexes that produce ATP.
34
cystic fibrosis
cause by loss of function mutations in CFTR gene. effects gene that codes for membrane protein that transports chloride ions in and out of cells. if chloride can’t leave cell, water doesn’t flow out of the cell and disrupts the normal balance of salt and water and results in the buildup of airway secretions.
35
huntington disease
from gain of function mutation that produces autosomal dominant disorder characterized by neurodegeneration. also results in uncontrollable mvmts, personality alterations and memory loss.
caused by expansion of triplet repeat - causes more glutamines to be inserted in the protein product and changes its function. results in cell death.
36
proto-oncogenes
non mutant versions of genes that control cell proliferation. a mutation that results in gain of function can alter a gene to an oncogene and cause hyperproliferation which can result in cancer. can be activated by: amplification (lots of extra copies of gene present), point mutation (leading to excessive cellular response), chromosomal translocations (novel gene created), transposition (gene moved from a relatively inactive area of chromatin to active area)
37
tumor suppressor genes
inhibit pathways that lead to cancer. mutation in tumor suppressor gene causes loss of function of product which can result in cancer. both copies of allele must lose function for cell to be affected. loss of function in a tumor sup. gene can occur through: deletion of portion of chromo with gene, point mutation w/in DNA sequence of gene, methylation of DNA that prevents gene from being transcribed.
38
gene therapy
to correct genetic mutations. affected gene can be identified and malfunction can be corrected through molecular manipulation. approaches:
## Footnote
* inserting a normal gene into genome to replace bad gene - most common
* replacing bad gene through homologous recombination
* repairing mutant gene by reversing original mutation
* altering regulation of a gene
39
nephron
functional unit of the kidney about 1 million in kidney
40
structure of kidney
cortex - outermost layer of the kidney (like the brain)
medulla - sits beneath cortex.
renal hilum - deep slit in center of medial surface. renal artery, vein, and ureter enter and exit through here.
renal pelvis - widest part of ureter, spans almost entire width of renal hilum. has portal system - 2 sets of capillaries in series that blood travels through before going back to heart.
2 sets of arterioles: afferent - lead to capillaries called glomeruli. efferent - branch out from them. Leads to vasa recta capillaries. (“A before E with C in between).
Bowman’s Capsule: cup like structure surrounding capillaries in the kidney. leads to a long tubule with: proximal convoluted tubule, descending and ascending limbs of the loop of Henle, distal convoluted tubule, and collecting duct.
41
Bowman’s capsule
cup like structure surrounding capillaries in the kidney. leads to a long tubule with: proximal convoluted tubule, descending and ascending limbs of the loop of Henle, distal convoluted tubule, and collecting duct.
42
kidney filtration
* some blood is filtered into the Bowman’s space - called filtrate.
* molecules or cells that are larger than glomerular pores will remain in the blood.
* first blood passes through glomerulus and into bowman’s capsule, then to efferent arterioles and through vasa recta.
43
filtrate
similar to blood, but doesn’t contain cells or proteins. filter can select based on size. anything that makes it to the filtrate and is not reabsorbed will be lost from the body. isotonic to blood so neither capsule or capillaries swell.
44
kidney secretion
* nephrons can secrete salts, acids, bases, and urea into the tubule with active and passive transport.
* kidneys get rid of ions or other substances that are in excess. excretes wastes that are too large to pass through glomerulus pores some filtered out compounds may be reabsorbed - ex. glucose, amino acids.
45
nephron function
* use osmolarity gradients and selective permeability to reabsorb things from the filtrate and selective excrete wastes.
* uses selective permeability in the different parts of the nephron.
* descending limb of loop of henle is permeable to water but not salt, ascending limb opposite.
* collecting duct almost always reabsorbs water but amount varies. hormones can alter permeability
* kidney can alter osmolarity of interstitium tissue around tubule. changes ability to absorb and excrete compounds.
* combo of osmolarity gradient and selective perm = **countercurrent multiplier system**
46
flow of filtrate
**proximal convoluted tubule:** glucose, amino acids, vitamins, majority of salts reabsorbed with water
**descending loop of Henle:** only permeable to water. concentration of surrounding tissues increases going down and drives water out of tubule.
**ascending loop of Henle:** permeable only to salt. filtrate moves up towards cortex, concentration in area drops and salt actively pumped out.
**distal convoluted tubule**: maintains same conc. as cortex by reabsorbing water and salt. final concentration depends on permeability of collecting duct. - influenced by ADH and aldosterone.
47
aldosterone
steroid hormone - secreted by adrenal cortex in response to decreased blood volume. also released by adrenal glands in response to increase in angiotensin.
alters ability of the collecting duct to reabsorb Na. increases blood volume and pressure.
48
ADH
antidiuretic hormone/vasopressin - peptide hormone.
changes permeability of collecting duct - allows more water to be reabsorbed by making cell junctions of duct leaky.
increased concentration of interstitium will cause reuptake of water from tubule.
made in hypothalamus, stored in posterior pituitary, secreted when blood osmolarity is high.
inhibited by alcohol and caffeine
49
kidney excretion
anything that doesn’t leave tubule is excreted. collecting duct = point of no return.
filtrate collects in renal pelvis after tubule. fluid is mostly urea, uric acid, and excess ions. fluid moves through ureter to bladder where it is stored. urine excreted through urethra.
shouldn’t have blood, protein, or glucose in healthy urine.
50
hepato-
prefix for things related to liver (think hepatitis=inflammation of the liver)
51
hepatic portal vein
delivers nutrients absorbed during digestion to liver.
52
what does the liver do to glucose
combines circulating glucose (when there is a lot) into glycogen to store and be broken down and released later as needed.
53
gluconeogenesis
liver can make new glucose from other things.
54
functions of liver
* glucose storage area
* deals with nitrogenous waste products.
* when glucose shortage - amino acids are used for cellular respiration and other important processes. go through deamination to be useful. prevent from forming ammonia by combination with CO2 → creates urea.
* detoxification
* storage of vitamins iron and B12 and cofactors
* destruction of old erythrocytes
* synthesis of bile.
* synthesis of blood
* proteins defense against antigens
* beta oxidation of fatty acids to ketones.
* interconversion of carbs, fats, and amino acids.
55
layers of skin (from outside in)
epidermis, dermis, hypodermis (subcutaneous level) derived from ectodermal germ layer
56
layers of dermis
papillary layer - has loose connective tissue reticular layer - below papillary layer
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functions of skin in homeostasis
protects from UV light. thermoregulation. transduction of sensory info from world. melanocytes - secrete melanin that protects from UV, DNA damage
58
thermoregulation
happens with vasodilation, vasoconstriction, and sweating.
sweating cools body.
pads of subcutaneous fat provide insulation from heat loss.
hair traps heat close to skin’s surface.
59
hypothalamus and temperature regulation
regulates body temp. in cold - stimulates blood vessels in skin to constrict to prevent heat loss, turns off sweat glands, shivering initiated.
if severe cold - will stimulate secretion of thyroid and adrenal hormones to increase metabolic rate
60
autocrine signaling
the same cell is stimulated. ex. some T-cells release interleukin-2 which binds to the same T-cell to increase immune functionality.
61
paracrine signaling
between cells that are close to eachother.
62
endocrine signaling
action at a distance. ex. FSH is released by the anterior pituitary but exerts its effects at gonads.
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endocrine organs capable of producing hormones
hypothalamus, pituitary, testes, ovaries, pineal gland, kidneys, gastrointestinal glands, heart, thymus.
64
hypothalamus
master control gland in brain. → like president
in forebrain between thalamus and pituitary.
regulates pituitary (paracrine) gets input from a lot of neural sources.
release of hormones regulated by negative feedback.
has anterior and posterior component - controlled in different ways.
65
hypothalamus interactions with anterior pituitary
hypothalamus secretes compounds into the hypophyseal portal system. hormones travel down pituitary stalk and bind to receptors in the anterior pituitary and stimulate the release of other hormones.
66
7 products of the anterior pituitary
FLAT PEG (FSH, LH, ACTH, TSH, Prolactin, Endorphins, GH) FLAT - tropic, PEG - direct
1st listed is hypothalamic hormone, 2nd is hormone released from anterior pituitary:
Gonadotropin-releasing Hormone (GnRH) → follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
Growth hormone-releasing hormone (GHRH) → growth hormone (GH)
prolactin inhibitory factor (PIF) → prolactin
thyroid -releasing hormone (TRH) → thyroid-stimulating hormone (TSH)
corticotropin-releasing factor (CRF) → adrenocorticotropic hormone (ACTH)
67
prolactin
opposite of most hormones in anterior pituitary that require factor from hypothalamus to be released. prolactin will not be released as long as the hypothalamus secretes PIF.
\*\*absence of PIF allows prolactin to be released. stimulates milk production in mammary glands.
68
controls on hormone release
feedback inhibition - hypothalamus and pituitary have receptors for secreted product in order to recognize when levels have changed.
69
feedback inhibition
aka negative feedback.
process by which the concentration of a product of intermediate in a metabolic pathway inhibits the pathway that led to its formation. used by enzymes and endocrine system.
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interactions b/w hypothalamus and posterior pituitary
not through hypophyseal portal system. neurons in hypothalamus send their axons down the pituitary stalk and into posterior pituitary. can release oxytocin and anti-diuretic hormone (ADH).
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direct hormones
bind to receptors on their target organs and have a direct effect (no intermediate is needed).
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tropic hormones
bind to receptors on organs and cause the release of effector hormones. act as intermediate.
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growth hormone
direct hormone
prevents glucose uptake in non-growing tissues and stimulates breakdown of fatty acids. this increases overall availability of glucose and allows growing muscle and bone to use it. in adults: works in smaller bones - bone remodeling
74
endorphins
direct hormone
decrease perception of pain.
mimiced by morphine
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posterior pituitary
contains nerve terminals of neurons whose bodies are in the hypothalamus receives and stores ADH and oxytocin from hypothalamus
76
thyroid gland
controlled by the pituitary (TSH) and hypothalamus (TRH) on front surface of trachea sets basal metabolic rate (controlled by thyroxine and triiodothyronine) and calcium homeostasis (controlled by calcitonin).
77
thyroid hormones
Thyroxine and triiodothyronine (T4 and T3) produced by iodination of tyrosine in thyroid. can reset metabolic rate by changing efficiency of energy production and altering utilization of glucose and fatty acids increased amt. = more cell respiration and protein and fatty acid turnover high levels will lead to decreased TSH and TRH synthesis.
78
important functions of calcium in the body
principal component of bone regulation of muscle contraction cofactor for normal blood clotting role in cell movement, exocytosis, and neurotransmitter release.
79
cells in thyroid gland
follicular cells - produce thyroid hormones C-cells - produce calcitonin
80
calcitonin
decreases plasma calcium levels by: increasing excretion from kidneys, decreasing absorption from the gut, increasing storage in bone. high levels of calcium in blood stimulate secretion of calcitonin from C-cells. “Calcitonin “tones down” Ca”
81
parathyroid hormone
PTH produced in parathyroid glands antagonistic hormone to calcitonin increases plasma levels of calcium by decreasing excretion of Ca through kidneys, increases absorption of Ca in gut, and increases bone resorption. activates vitamin D - required for absorption of Ca in the gut. decreased with increased levels of plasma calcium.
82
adrenal glands
at top of kidneys have cortex and medulla cortex: secretes set of hormones called corticosteroids
83
corticosteroids
steroid hormones - derived from cholesterol three types: glucocorticoids, mineralocorticoids, cortical sex hormones. (three s’s: sugar, salt, and sex)
84
glucocorticoids
cortisol and cortisone raise blood glucose by increasing gluconeogenesis and decreasing protein synthesis. can decrease inflammation and immune responses. cortisol - released in response to stress; affects several areas of the body.
85
mineralocorticoids
coordinate with kidneys to control salt balance aldosterone: causes increased reabsorption of sodium and water, leading to higher blood pressure. also affects levels of potassium and H ions.
86
cortical sex hormones
adrenals can make male sex hormone (androgens) large secretion of androgens happens in testes in men, but in women the secretion from the adrenals is important. can increase male sex characteristics in men (ex hair growth)
87
adrenal medulla
responsible for production of epinephrine and norepinephrine (fight or flight hormones) have special nerve cells that secrete these directly into circulatory system. hormones increase activity of body systems needed for fight or flight and decrease activity of rest and digest systems. conversion of glycogen to glucose in liver and muscle, increased metabolic rate, increase heart and resp rate, alter blood flow to supply necessary systems and decreased to others.
88
endocrine function of pancreas
islet of Langerhans- special group of cells with alpha, beta, and delta cells alpha - secrete glucagon, beta - produce insulin, delta make somatostatin.
89
glucagon
hormone with antagonistic actions to insulin. secreted during famine to stimulate degradation of protein and fat., converting glycogen to glucose, production of new glucose via gluconeogenesis. “glucagon secreted when glucose is gone!’”
90
insulin
levels rise in conjunction with blood glucose levels induces muscle and liver cells to take up and store glucose as glycogen stimulates anabolic processes such as fat and protein synthesis
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somatostatin
inhibits insulin and glucagon. stimulated by high blood glucose and amino acid concentration
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testes
site of spermatogenesis happens through interplay of FSH and LH
FSH- stimulates Sertoli cells and necessary for sperm maturation
LH- causes testosterone production - necessary for male embryonic differentiation, sex development at puberty, and maintenance of sex characteristics.
93
ovaries
under control of FSH and LH secreted from anterior pituitary. produce estrogen and progesterone
94
estrogen
secreted in response to high levels of FSH and LH responsible for development and maintenance of secondary female sex characteristics. lead to thickening of endometrium each month stimulate development of female reproductive tract in embryos secreted by ovarian follicles and corpus luteum
95
progesterone
secreted in response to LH stimulation released from corpus luteum responsible for development and maintenance of the endometrium by end of first trimester - progesterone supplied by the placenta
96
phases of menstrual cycle
follicular phase, ovulation, luteal phase, and menstruation.
97
follicular phase
begins with menstrual flow - sheds lining of previous cycle GnRH secretion from hypothalamus increases. → causes increased secretions of FSH and LH. develop ovarian follicles that begin to produce estrogen and lowers GnRH, LH, and FSH levels
98
menstrual cycle
follicles mature during follicular phase (FSH, LH) LH surge at midcycle triggers ovulation ruptured follicle becomes corpus luteum and secretes estrogen and progesterone to build up uterine lining for implantation; LH and FSH inhibited. if fertilization doesn’t occur, corpus luteum atrophies, progesterone and estrogen levels decrease, LH and FSH levels rise again.
99
when do FSH, LH, estrogen, and progesterone peak during menstrual cycle
FSH & LH - mid cycle, at ovulation estrogen - late in follicular phase progesterone - luteal phase
100
ovulation
induced by surge in LH. ovum released from ovary into abdominal cavity.
101
luteal phase
LH causes ruptured follicle to form corpus luteum c.l. secretes progesterone which maintains uterine lining for implantation. high levels of estrogen and progesterone cause neg. feedback on GnRH, FSH, and LH to prevent development of multiple ova.
102
menstruation
if implantation doesn’t happen, human chorionic gonadotropin hCG won’t be made and progesterone levels decline and the uterine lining is sloughed off.
103
pineal gland
deep in brain. secretes melatonin. may be involved in circadian rhythms.
104
types of hormones
peptide, amino acid derived, and steroid. based on chemical structure
105
peptide hormones
made up of amino acids charged, can’t cross cell membrane act as first messengers by binding to receptors on exterior of cell. stimulate second messengers (like cAMP) → signaling cascade can bind to multiple receptors before being degraded effects usually short lived quicker to turn on and off compared to steroid hormones.
106
steroid hormones
all derived from cholesterol can easily cross cell membrane. dimerize when binding receptor (pair with another receptor-hormone complex) longer lived effects alter amt of mRNA and protein in cell. takes longer to see their effects intracellular receptors hormone receptor binding to DNA promotes transcription of specific genes
107
amino acid derivative hormones
less common include epinephrine, norepinephrine, and thyroxine. can act as second messenger systems or acti like steroid hormones in cell (depending on polarity of molecule)
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thymus gland
secretes hormones that stimulate T lymphocyte development and differentiation. atrophies by adulthood after immune system has fully developed.
109
polycistronic
prokaryotic mRNA and its ability to code for more than one polypeptide - usually a group of related proteins.
110
trp operon
transcription is the norm as long as there is no co-repressor present. the co-repressor binds to the repressor, forming a complex that binds to the operator and prevents transcription.
111
lamark’s theory of evolution
first organized approach to evolution, was wrong “use and disuse of inheritance of acquired characteristics” organs that were used by a species would develop, and those not used would atrophy → acquired characteristics
112
Darwin’s theory of natural selection
\*\*\*evolution is not equivalent to natural selection - just a mechanism for evolution.\*\*\*
tenets:
* chance variations occur as a result of mutation and recombination
* if variation is selected for by the environment, individual will be more fit and more likely to survive to reproductive age
* survival of the fittest leads to an increase of those favorable genes in the gene pool
113
neo-darwinism (the modern synthesis)
update of Darwin’s theory to include info that genes change due to mutation and recombination. → process is called differential reproduction. traits passed on by more successful organisms will become pervasive in gene pool
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punctuated equilibrium
changes in some species occur in rapid bursts rather than evenly over time.
115
evidence of evolution
paleontology - relating ages of fossils to their anatomies and abundances can help determine succession of species in time biogeography - species evolve differently in different places - ex. galapagos. comparative anatomy - comparing similar structures between species helps determine evolutionary similarity between them. comparative embryology - analyzing similarities between embryos of different species molecular bio - comparing DNA between species.
116
homologous, analogous, and vestigial structures
homologous - similar in structure and share common evolutionary origin. analogous - serve common purpose by evolved separately vestigial - remnants of organs that have lost their ancestral function.
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Hardy-weinberg equilibrium
population must meet 5 criteria:
1. population is very large
2. no mutations that affect gene pool.
3. mating between individuals in population is random
4. no net migration in or out of population
5. genes in population are all equally successful at reproducing pair of
equations to predict the allelic and phenotypic frequencies:
p+q=1 → tells frequency of alleles.
p2+2pq+q2=1 → tells frequency of phenotype in population.
p=frequency of dominant allele (T)
q=frequency of recessive allele (t)
p2= frequency of dominant heterozygotes (TT)
q2= frequency of (tt)
2pq = frequency of (Tt)
\*\* remember there will be twice as many genes as people in the population because each person has two copies of autosomal genes.
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microevolution
natural selection - genotypes with favorable variations are selected through natural selection. mutation - gene mutations shift equilibrium by changing allele frequencies in population assortive mating - if mates not chosen randomly, genotype ratios will be affected genetic drift - changes in the composition of gene pool due to chance. gene flow - migration of individuals between populations will result in loss or gain of genes.
119
stabilizing selection
keeps phenotypes in a specific range by eliminating extremes. (ex. birth weight)
120
directional selection
adaptive pressure leads to emergence and dominance of an initially extreme phenotype. (ex. DDT resistant mosquitoes)
121
disruptive selection
both extreme phenotypes selected over the norm.
122
altruistic behavior
some species selflessly sacrifice for the benefit of others. (ex. ants)
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speciation
emergence of a new group of individuals who can interbreed freely with each other, but not with members of other species.
124
prezygotic isolation mechanisms
prevent formation of zygote between two different species.
can be:
temporal (breed at different times) ecological (different habitats - rarely meet) behavioral (not sexually attracted to each other) reproductive (incompatible genetalia) gametic (fertilization can’t happen)
125
postzygotic isolating mechanisms
allow for gamete fusion but result in inviable or sterile offspring. can be: hybrid inviability (genetic incompatibilities abort zygote) hybrid sterility (offspring are sterile) hybrid breakdown (first gen. hybrids are viable, but 2nd gen aren’t - happens with closely related species, more in plants than animals.
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patterns of evolution
convergent: independent development of similar characteristics in 2+ lineages without common ancestor
divergent - independent development of dissimilar characteristics in two or more lineages sharing common ancestry.
parallel: related species evolve in similar ways for a long time in response to analogous environmental selection pressures.
