species: Keystone a species that is not necessarily abundant but exerts strong control over
community structure.
Indirect effects
Trophic cascade: alternating positive and negative effects caused by the consumption of a species
at a different trophic level. For example, the consumption of a species at next level will reduce
pressure caused by that species on the next lower species.
Killer whale predation on sea otters has decreased populations 5 fold.
Over harvesting of sharks has increased its prey and decreased the preys prey.
How communities of many species interact. How is species diversity maintainedhow are
dominant players restrained from forming monocultures (keystone predators)?
Disturbance: something that occurs that destroys individuals or biomass from a community
usually by altering resource availability. Patterns determined by projecting long term patterns
from short term analysis and by looking at the history of a particular site
Disturbance regime: type, frequency, and severity of disturbance
Fire opens up the pine cones that are shut with resin and that contain the seeds.
Primary succession: succession that occurs in a lifeless area where no organisms had existed and
where soil had not yet formed. (example, glacier slides and leaves moraines which are sites for
primary succession)
Secondary succession: the removal of all of the organisms but leaving the soil intact through a
disturbance. The sequence of species that follow is a successional pathway
Pioneering species: organisms to first arrive in a disturbed site, have good dispersal ability
Facilitation: existing species make conditions more favorable for subsequent species
Tolerance: existing species do not affect establishment of subsequent species
Inhibition: one species affects establishment of another
Gleason: argued that the development of a community after a disturbance is random, a matter of
chance whether or not the new community is similar to the old
Species area theory: under equal circumstances, the larger the geographic area, the more species.
As latitude increases, species diversity increases. Communities in tropics (equator) have more
species than in temperate/subarctic
High productivity hypothesishigh productivity=high diversity
Energy hypothesistemperature affects productivity and ability of organisms
Tropical regions have had more time for speciation than in other regions
Intermediate disturbance hypothesis: moderate type, frequency, and severity of
disturbance=high species richness and diversity
Trophic levels in food web important:
Earths energy can support more herbivores than carnivores.
Biomagnification: when an artificial/synthetic chemical is passed on between tophic
levels and it is stored and concentrated rather than excreted. More levels in food chain
increases potential for concentration
Clostridium botulinum: a decomposer, anaerobic bacterium that is very toxic to humans
Dead algae promote growth of C. botulinum, mussels filter out algae, clarifying water and
promoting even more algae growth. Mussels ingest botulism toxin, not affected by it. Gobies
devour mussels and become paralyzed; birds eat gobies, become paralyzed and drown.
Behavior: everything an animal does and how it does it (from hunting to mating). Innate and
learned
Some types of behaviors can be modified by learning, other cannot
Fixed action pattern: stereotyped behavior that does not vary, is species specific, continues until
completion. Responses to stimuli (releasers)
Classical conditioning: individual trained to give same response to more than one stimulus, even
one that has nothing to do with normal response (dog salivation at sound of bell)
White crowned sparrow can only learn their specific song during a critical period. If they do not
hear a song, they do not learn how to sing. After learned, cannot be changed by further learning
Cognition: recognition and the manipulation of the world and to use this to form concepts
Hamiltons rule: The principle that for natural selection to favor an altruistic act, the benefit to
the recipient, devalued by the coefficient of relatedness, must exceed the cost to the altruist
Inclusive fitness: the total effect an individual has on proliferating its genes by producing its own
offspring and by providing aid that enables other close relatives to increase the production of
offspring
Foraging: behavior to recognize, search for and obtain food. Crow dropping mollusks at optimal
height to crack shell
Honeybee dance, round dance to direct workers to food close to hive, and waggle dance to direct
workers to food further away
Migration
Alaskan chickadees must eat 1/10 of body weight during winter to survive winter climate
Blackpoll Warbler eats enough to get itself through migration. Use sun and magnetic field to
navigate during day and Polaris to navigate during night
Population: group of individuals from same species that live in same area at the same time
Population ecology: how population changes over time dynamics of population change.
Affected by number of individuals in population, immigrants (increase population), death,
emigration
Demography: how these dynamics are measured life table
Life table: a look at a population, a summary of the probabilities of survival and reproduction in
any given year over the life time of the individual
Fecundity: average number of female offspring produced by each female
Survivorship: always decreases over time. But fecundity will respectively increase. Proportion
of offspring that will survive to a particular age
Survivorship curve: type 1: good chance of survival until at least middle age, then decline
rapidly. Type 2: odds of dying constant life. Type 3: die quickly heavy mortality
Life history: how organism allots resources for growth, reproduction, and survival. Trade off
between survival and reproduction because of limited resources at disposal of individual (high
fecundity, low survivorship.low fecundity, high survivorshipmoderate/moderate)
Kestrel experiment: the more offspring, the more parents will care for them, the lower
survivorship
In a closed population (no emigration/immigration), the per capita rate of increase is just the
difference between birth and death rates.
Intrinsic rate of increase: property of species/population in which b is as high and d is as low as
possible. dN/dt=rmaxN
Density independent: does not matter how many individuals you have, r remains constant. Tend
to be abiotic (storms, weather patterns, climate change). Change birth/death rates regardless of
population size
Density dependent: r declines because r does depend on population at a given time. Gives way
to the concept of carrying capacity (K) which is the maximum number of individuals in a
population that can be supported in a particular habitat over a period of time. If N reaches K, the
growth will stop, if N<K, growth will continue. As population reaches carrying capacity, r goes
to 0. Biotic factors (predation rates. Change in intensity as a function of population size).
Affects survivorship and fecundity causing logistic population growth
Metapopulation: populations of populations . Individuals are congregated in patches to form
small isolated populations. Immigration and emigrations are important here
Zero population growth: each woman producing exactly enough offspring to replace herself and
her offsprings father. Every graph will approach this
Exponential population growth tends to overshoot carrying capacity before stabilizing
Genome: all of the chromosomes
Sequences of 4 nucleotide bases (GATC) + associated proteins=chromosomes
Cell replication: duplication of all stuff in cell necessary for subsequent cells to function, then
physically separate duplicate stuff into 2 daughter cells
Eukaryotes are more complex and larger then are prokaryotes. Prokaryotes do not have a
membrane bound nucleus like eukaryotes do
Plasmids: bits that carry genes
Prokaryotes: binary fission: Bacteria and Achaea division: chromosome replicates, move apart,
ring constricts cell wall and separates (fission)
In Eukaryotes, there are many chromosomes that need to be replicated instead of in prokaryotes,
where there is only one.
Eukaryotes: Mitosis: process by which we begin with a cell with a single genome and replicate it
and pass it onto daughter cells so that they have identical to parental cell
Asexual reproduction: standard mode of reproduction in prokaryotes. There are modes to
exchanging bits of information. Clonal reproduction (clones of parents)
Sexual reproduction: separating diploid into haploid and fusing them back together
Interphase: when cell is not dividing, it is still doing what a cell does, when chromosomes are
unwound, dna being transcribed into RNA, goes to ribosomes to produce proteins
G1 phase: after mitosis and before next round of synthesis. Chromosomes are unwound, making
proteins, cell doing its thing
S phase: DNA synthesis occurs, 2 copies will exist at the end of the s phase. Each copy is called
a chromatid. The 2 replicated chromatids are still connected to form a chromosome
G2 phase: after S phase and before mitosis
Mitosiscytokinesis
Sister chromatids are attached by centromere right before cytokinesis
Motor proteins attach onto cytoskeleton at microtubules and encourage the process of cytokinesis
through contractions.
Centrosomes: create spindles that organize chromosomes. Form during interphase
Mitosis
Prophase: chromosomes condense and spindle forms
Prometaphase: chromosomes come out of nucleus and connect to spindle fibers at
kinetochores
Metaphase: chromosomes aligned along metaphase plate (middle of cell)
Anaphase: spindle fibers now reeled in by motors, pulling separates sister chromatids
(now called chromosomes)
Telophase: nuclear envelope forms
Cytokinesis: cell division begins while an actin-myosin ring pinches the plasma
membrane.
During embryo: With quick cell proliferation that excludes the Gap phases, the daughter cells
become smaller and smaller. Each cell is communicating with all cells around it allowing all of
them to grow in a particular fashion around yolk
Some cells have to replicate all of the time in the body because of normal wear and tear. Most
cells do not divide anymore.
Stem cells: a small fraction of human cells that can differentiate cell division into subsets of
differentiated cell types (i.e. blood stem cells in bone marrow)
Cell-cycle checkpoint: critical step that regulates cell cycle
Tumor suppressors: non dividing cells enforced by proteins can that stop the cell cycle. If it is a
stem cell, the G1 checkpoint can be passed if the cell size is adequate, nutrients are sufficient,
social signals are present, and DNA is undamaged. G2 checkpoint can be passed if
chromosomes have replicated successfully. Metaphase checkpoint can be passed if all
chromosomes are attached to spindle apparatus
Cancer: when checkpoints break down and cells that should not be dividing actually do. This is
cancercell division out of control. Mortality factor
Benign tumors: noninvasive
Malignant tumors: invasive and can spread throughout body
Most cancers result in multiple mutations in regulatory cell cycle
Sexual reproduction meiosis: reduce amount of genetic information down to half as much that
will be sequestered into gametes (eggs and sperm) which will be fused again in zygote to restore
the genetic information
Asexual lineages are all female clones. This is more efficient production than sexual production
because you dont have to produce males. Why does meiosis/sexual production predominant
among multicellular animals?
Sexual reproduction helps organisms to evolve faster by constantly generating genetic
novelty. This will give them an edge over co-adapted parasites and pathogens. Influences
evolution of animals and plants, shaping genetic structure, morphology and behavior
Whiptail lizards, for the most part, reproduce asexually. Asexual vertebrate rapidly go extinct
Haploid: 1 set of chromosomes, Diploid: 2 sets of chromosomes
Meiosis restricted to germ cells whereas mitosis restricted to somatic cells. Germ cells located
in gonads and undergo meiosis to produce haploid (1 set of chromosomes) cells called gametes
that pass on genetic info to next generation of organisms
Human karyotype is diploid (2 haploids fused, one from mother and other from father)
Meiosis starts with a diploid cells, ends up with haploid cell. S phase replicates chromosomes.
1st division (meiosis 1) separates chromosomes (homologs, daughter cells contain just one
homolog), 2nd division (meiosis 2) separates chromatids (now 4 daughter cells contain one
chromosome each, becomes gametes).
Interphase: precedes Meiosis 1, cell replication occurs here. Only time during meiosis during
which cell replication occurs
Meiosis 1:
Early Prophase 1: tetrad (4 chromatids from homologous chromosomes paired up).
Spindle forms. Chromosomes coil and become shorter
Crossing over: parts of arms of 1 chromatid exchange with arms of another chromatid.
Outside chromatids remain the same, but the inner 2 chromatids are recombinant, have
different alleles
Metaphase: chromosomes align along metaphase plate
Anaphase: chromosomes pulled apart by fibers
Telophase & cytokinesis: two haploid cells produced (2 chromosomes in each)
Crossing over: homologous pairs of duplicated chromosomes are aligned to form tetrads,
exchange chromosome segments at sites called chiasmata. The longer the chromosomes, the
more chiasmata and hence the more crossing over. Produces chromosomes that are unlike either
of the parents
Independent assortment: when each pair of chromosomes sorts its maternal and paternal
homologues into daughter cells independently of other pairs. This does not include crossing
over, has only to do with probable arrangements of whole chromosomes during metaphase I
Meiosis 2: happens right after meiosis 1
Prophase 2: spindle forms
Metaphase 2: chromosomes line up at metaphase plate
Anaphase 2: sister chromatids separate
Telophase 2 and cytokinesis: chromosomes move to poles of cell, divides
Random fertilization: 3rd level of genetic diversification (gametes combine to make zygote)
True breeding: yielding non variant offspring (dominant/recessive homozygous)
Mendel used a large sample size, followed inheritance over multiple generations, picked
characteristics that displayed discrete traits (white/purple, not in between), repeated self
fertilization to develop true breeding lines
Type of gamete not important with respect to inheritance
Principal of segregation:
inheritance of each trait determined by genes that are passed on to descendants
unchanged.
Variations due to the presence of different alleles.
The gamete will only carry one gene during gamete formation
An individual inherits one copy of genes from each parents. True breeding (same) or
hybrid (different morecomplex)
If they differ (hybrid), one is fully expressed (dominant) and the other is masked
(recessive)
(most controversial to originally accepted theoryblending inheritance). Two copies of
gene that every individual has (one from mom, one from dad) will separate randomly
during gamete formation and so the gamete will only carry one gene. Recessive trait can
be expressed later on.
Dihybrid crosses: matings between parents heterozygous for 2 traits
Hypothesis of dependent assortment: dihybrid cross yields the same results as a monohybrid
cross. Alleles of different genes stay together when gametes form
Hypothesis of independent assortment: alleles of different genes dont stay together when
gametes form. Inheritance of alleles are independent of each other
Chromosome theory of inheritance: mendels rules can be explained by the independent
alignment and separation of homologous chromosomes at meiosis I (they match)
Balanced polymorphism: a harmful allele resulting from mutation will stay around in a
population if heterozygote has a selective advantage over homozygous recessive/dominant.
These traits are when heterozygotes protect against an infectious disease, the homozygotes die
from the disease
Malaria: recessive gene is okay if in presence of dominant allele. However, homozygous
recessive will lead to sickle cell anemia. The recessive sickle cell allele grants immunity to
malaria EXAMPLE OF BALANCED POLYMORPHISM
Nettie Stevens: discovered Y chromosome and correlated it to males
Thomas Morgan: worked with fruit flies with Nettie and discovered a mutant male with white
eyes. Found 3:1 ratio red:white in F2, but only occurs in male F2 flies
Autosomes: non sex chromosomes that carry the same genes
Heterogametic sex: males are XY
Homogametic sex: females are XX
X-linked inheritance: Gene for white eye color is on the x chromosome, y chromosome does not
have the gene. Hence, females would have 2 copies of genes and males only have 1. The mutant
genotype (white eyed) is rare and recessive, less common in females
X chromosome is larger and has much more genes on it than on Y chromosomes and so any male
that receives X chromosome from mother will express the genes on that X chromosome
X linked: color blindness, muscular dystrophy, hemophilia
Genes on different chromosomes are inherited independent of each other (according to law of
independent assortment) because the chromosomes separated into independent independently
Linkage: if chromosomes are linked, going to violate independent assortment. Independent
assortment does not apply to linked genes, linked genes separate together except when crossing
over
Recombinant genotypes: combinations of alleles on chromosomes of daughter cells that differ
from the combinations present in parents. Due to crossing over
If genes are on the same arm of chromosome but far each other, there will always be a crossing
over even in between them. 50 or more map units apart on same chromosome, behave as
independent genes and assort independently
Incomplete dominance: heterozygotes have an intermediate phenotype
Polyallelic: 3 alleles of the enzyme that attach carbs to red blood cells
Codominance: both phenotypes are express. Recessive allele does nothing
Pleiotropy: when a single gene can have multiple phenotypes
Epistasis: interaction of different alleles at different loci that produce different phenotypes
Hardy Weinberg model: calculates allelic frequencies for a particular gene to see if a population
is evolving with respect to that particular trait
Incomplete dominance: heterozygotes have an intermediate phenotype (flower can be pinke,
white, and red)
Polyallelic: more than 2 alleles (blood type)
Codominance: both phenotypes are expressed (when IA and IB are together, both carbohydrates
will be present)
Epistasis: one locus (B/b) determines hair color, second locus (C/c) determines if pigment will be
deposited in growing hair
Environmental effect:
Polygenic: trait that is accounted for by many genes. Skin color
Gene pool: all of the genes and their alleles present in a population at a certain time.
Gene flow: addition of or subtraction from a population (immigration/emigration), moving
gametes from one population to another. Begins to maintain genetic coherence of the species as
well as similar allele frequencies
Mutation: change in nucleotide bases, rare and random and typically deleterious
Genetic variation due to sexual recombination (crossing over, independent assortment, random
fertilization between gametes). Counterintuitive: Tend to preserve genetic variation between
generations
Hardy-Weinberg Principle: after one generation of random mating, genotype frequencies for 2
alleles at a locus will be p^2 + 2pq + q^2. Reproduction does not change frequencies of alleles
from one generation to another reshuffles alleles, but frequencies remain constantThere are
no populations that fulfill these criteriahence all populations MUST go through evolution. In
order for this equation to be used, the population must be ideal and follow the following
guidelines:
Random mating
Infinitely large population
Closed population
Alleles are static, no natural selection
Equal probabilities of reproduction among individuals
Locus is not x-linked
No mutation
Genetic drift: unpredictable fluctuations in allelic frequencies from one generation to the next
based largely on sampling size (small populations will not be able to contain as many alleles as
could a large population)
Founder effect: a small group with a different alleilic frequency from the source leaves the
source population and colonizes new habitats
As we move further from Africans, we become less genetically diverse. Early humans
represented a series of founder effects when they left Africa
Bottleneck effect: change in genetic diversity caused by random catastrophic change in
population that may lose many alleles. Some of the alleles may not have made it out of the
bottle. Low genetic variation
Inbreeding: mating between relatives, reduces frequency of heterozygosity by increasing the
frequency of homozygotes. Have less fitness as more recessive traits are expressed
homozygously