Knowt
tri 2 exam (units 6-8)
Unit 6 - Ch 1
EQ: What is the structure of DNA, and how do we know?
Early Hunt for genetic material
Morgan (fruit fly guy) showed that genes are located on chromosomes, so DNA and protein became candidates for the genetic material (both part of chromosomes)
First experiments
The genetic role of dna began w research by frederick griffith in 1928, who worked w different strains of bacteria, both harmless and pathogenic
Griffith’s conclusion
When heat-killed pathogenic strain was mixed with living cells of harmless strain some living cells become pathogenic
He called it transformation now to find as a change in genotype and phenotype due to uptake of foreign chromosomes
More evidence
bacteria can be infected by viruses or bacteriophages or phages
a virus is DNA or RNA enclosed by protective protein code that infects cells and takes over the cell's metabolic Machinery in order to reproduce
Hershey and Chase
in 1952 Alfred Hershey and Martha Chase showed that DNA is the genetic material of the phage known as T2
experiment show the only the DNA of the phage not the protein enters an E coli cell during infection
Conclusion: DNA is genetic material (not proteins)
More evidence for DNA new line
in 1950 Erwin chargaff reported that difference species have different DNA so now we have chargaff's rules:
base composition of DNA varies between species
in any species the percentages of A&T bases are equal and the percentages of G and C bases are equal
Discovering the structure of DNA
in 1953 James Watson and Francis (Rick were working on DNA structure while Maurice Wilkins and Rosalind Franklin were using x-ray crystallography to study molecular structure
Building the structural model of DNA new line
Franklin's x-ray images of DNA led to Observation that DNA was helical
photo 51 also suggested that the DNA molecule was made of made up of two strands forming a double helix
Franklin concluded that there were two outer sugar phosphate backbones with the nitrogenous base bases paired in the interior
Watson built a model in which the backbones were antiparallel (they're subunits run in opposite directions)
At first it was thought base bases paired like with like a with a g with G Etc but this model did not result in uniform with
instead pairing of pyramid with purine with pyrimidine resulted in uniform with consistent with x-ray data
Found that adenine a parent only with thymine tea and guanine G parent only with cysto sign C
relates to chargaff's rules
hydrogen bond: only by nitrogenous pairs
Unit 6 - Ch 2
EQ: How does DNA replicate?
Structure versus function
Double helix is the key new line
specific base pairing suggested a possible copying mechanism for genetic material
Base pairing to a template strand
since two strands of DNA are complementary each strand stores the information necessary to reconstruct the other
this semi-conservative model predicts that when DNA replicates each daughter molecule will have one old strand conserved from molecule and one newly made strand
Getting started
replication begins at sites called origins of replication where the two DNA strands are separated opening up a replication “bubble”
at each end of a bubble is a replication for a y-shaped region where the parental strands of DNA are being unwound
Replication DNA a closer look new line
more than a dozen enzymes and other proteins participate in DNA replication new line
enzymes and DNA replication: helicase unwinds parental double helix, binding proteins stabilize separate strands, primase adds short primer to template strand, DNA polymerase Vines nucleotides to form new strands, DNA polymers one exonuclease removes RNA primer and inserts the correct basis, ligase joins okazaki fragments and seals other Nick's in sugar phosphate backbone
Synthesizing new DNA strand new line
enzymes that synthesize DNA cannot initiate synthesis of a new polynucleotide they can only add nucleotides to an already existing chain
the initial nucleotide strand is a short RNA primer 5-10 nucleotides the enzyme primates starts an RNA chain with a single RNA nucleotide and adds RNA nucleotides one at a time using parental DNA as a template
enzymes called DNA polymerase catalyzed the elongation of new DNA out of replication for by adding nucleotides to the 3-in end of a pre-existing chain
the ray of elongation is about 500 nucleotides per second in bacteria and 50 per second and human cells
Antiparallel elongation continuous
newly replicated DNA strands must be formed to antiparallel to the template strand because DNA polymerase and to add nucleotides only to the free 3-in end of a growing strand so the Strand can elongate only in five inches to 3 in Direction
along the template strand DNA polymerase three synthesizes of leading strand continuously moving towards the replication fork with only one primer needed
antiparallel elongation -discontinuous
to elongate the lagging strand DNA polymerase most work in the direction away from the replication fork
This is synthesized as series of segments called Okazaki fragments 100 till 200 nucleotides long in eukaryotes and 1,000 till 2,000 nucleotides long and E coli
polymerase one removes RNA primers and replaces with DNA remaining gaps or joined together by DNA ligase
evolutionary significance of altered DNA nucleotides
the error rate after proofreading repair is extremely low but not zero. sequence changes may become permanent and can be passed Onto the Next Generation
these changes mutations are the source of genetic variation upon which natural selection operates
Unit 6- Ch 3
EQ: how are genes expressed?
Central Dogma (PS)
Explains the flow of genetic information… instructions in DNA are converted to a functional product (DNA to RNA protein)
RNA versus DNA new line
RNA is the bridge between DNA and protein synthesis
RNA is chemically similar to DNA but RNA has:
ribose instead of deoxyribose
uracil (U) instead of find thymine (T)
one strand instead of two
Two steps of protein synthesis
transcription- synthesis of mRNA using info and DNA happens in nucleus
translation- synthesis of polypeptide using info in mRNA happens in ribosomes
prokaryotic / bacterial versus eukaryotic
translation of mRNA can begin before transcription has finished
RNA transcripts are modified through RNA processing to yield the finished mRNA new line
mRNA must be moved out of the nucleus
Transcription new line
Promoter
Upstream from coding region new line specific DNA sequence new line serves as attachment site for transcription molecules new line sequence is not transcribed into RNA
RNA coding region
Terminator
Downstream from coding region new line is transcribed into RNA sequence is later removed new line specific sequence to Halt transcription
mRNA processing
5 in methyl cap ( to help mRNA move through nuclear pores and attached to ribosome) and 3-in poly a tail to prevent degrade degradation of the MRNA are attached
introns non-coding portions of DNA are removed and then remaining exons coding protons are spliced together
Translation new line
initiate decrease of initiation transitional complex forms and TRNA brings first amino acid in polypeptide chain to bind to start codon on mRNA new line
Elongation: TRNA brings amino acids one by one to add to polypeptide chain
Termination: release Factor recognizes stop codon transitional complex disassociates and completed polypeptide is released (components are recycled)
micro RNA (miRNA)
21/23 nucleotides long
non-coding RNA molecules that regulate gene expression by controlling protein formation new line
bind to mRNA in cytoplasm to delay / prevents translation
codons Triplets of nucleotides
nucleotides are red in groups of three to specify 20 amino acids
Triplets of DNA nucleotides are transcribed into messenger RNA codons of mRNA and then translated by anticodons of TRNA to sequence amino acids forming a polypeptide new paragraph
DNA templates new line
only one of the two DNA strands is a template strand to produce template for ordering the RNA transcript new line
template strand is always the same strand for any given gene. however Elsewhere on the chromosome the opposite strand May function as a template for a different Gene
cracking the code
total of 64 codons but only 61 code for amino acids and three triplets are stop signals to end translation
each colon only specifies one amino acid
codons must be read in the correct reading frame or like to correct groupings in order for specific polypeptide to be produced
codons are red one at a time in a non overlapping fashion
AGU/CUU/
A/GUG
AG/UCU
Evolution of the genetic code new line
the genetic code is nearly Universal shared by the simplest bacteria and the most complex plants and animals
genes can be transcribed and translated after being transplanted from one species to another
Unit 6 - Ch 4
EQ: how is gene expression regulated in prokaryotes?
*Genes are now defined as…
A region of DNA that can be expressed to produce a final functional product either a polypeptide or an RNA molecule for both euks and prokes
Prokaryotic genes are regulated by operons —> groups of genes controlled by a single promoter
EX: bacterial E coli lives in a in gut and eats whatever you eat lactose and tryptophan
For operons: PROG
Entire stretch of DNA that includes promoter regulator operator genes
A single promoter RNA polymerase attachment site serves a set of functionally related genes
genes can then be coordinately controlled by single on off switch which is a segment of DNA called an operator
Operon Is controlled by repressor
protein that binds to operator and blocks advancement of RNA polymerase
product of separate regulatory Gene which is used to make proteins but is not connected to the operon and possibly quite distant from from the Opera on itself
can be active or inactive depending on presence of other molecules like a co-repressor which is a molecule that cooperates with the repressor to control an operon
two types of negative Gene regulation prevents binding of RNA polymerase
an inducible operon is one that is usually all fun inducer can inactivate the repressor to turn it on
example: lac operon is an inducible operon regulates lactose new line a repressible operon is one that is usually on but repressor can turn it off new line
example trip operon is responsible or repressible operon regulates tryptophan
inducible lac operon
contains genes that code for enzymes that function in the use of lactose new line by itself black repressor is active and switches the lac operon off by binding the operator new line a molecule called in inducer hello lactose inactivates the repressor to turn the lac operon on
repressible equals trip operon
contains genes that code for enzymes that help produce tryptophan new line by itself the trip repressor is inactive and keeps the trp operon on by not binding the operator new line a molecule called core repressor tryptophan activates the repressor to turn the trp operon off
tryptophan is one of the 20 amino acids
if present trip binds to the repressor which can then bind to the operator thus turning off the operon
positive Gene regulation enhances binding of RNA polymerase new line E coli prefer to use glucose but if glucose runs low it needs to use more lactose new line the c a m p receptor protein CRP acts as an activator protein of transcription by binding with cyclic amp
activate CRP attaches to promoter and makes RNA polymerase bind butter does accelerating transcription
when glucose levels increase new line cam levels fall CRP detaches from the Lac operon and transcription proceeds at a lower rate
Erp also helps regulate other operons on code enzymes used in catabolic Pathways and may affect the expression of more than 100 genes in E coli
Unit 6 - Ch 5
EQ: how is eukaryotic gene expression regulated?
In all organisms gene expression is commonly controlled at transcription but the greater complexity of eukaryotic cell structure and function provides opportunities for regular regulating gene expression at many additional stages
eukaryotic transcription regulation RNA polymerase needs to bind to a promoter example t a t a box common youth promoter
eukaryotic RNA polymerase also requires the assistance of transcription factors activators and enhancers
DNA bending proteins curve the double helix structure so that distant activators enhancers come in contact with the transcription factors creating a transcription initiation complex
EQ: How do mutations in DNA affect protein structure and function?
mutations new line
changes in the genetic material of cell that occur during DNA replication recombination or repair
Point notation only one nucleotide switched for another is called a substitution may or may not lead to production of abnormal protein
point mutation can be transmitted to offspring if it occurs in a gamete egg or sperm
point mutation effects new line
silent mutations have no effect on the amino acid new line
nonsense mutations change in amino acid codon into a stop codon usually creating a non-functional protein
missense mutations change one amino acid to another
conservative equals AA with similar properties to original
non-conservative equals AA with different properties from original
insertions and deletions
insertions and deletions are additions or losses of nucleotide pairs in a gene and can alter the reading frame of the genetic message producing a frameshift mutation
mutagens new line physical or chemical agents that can cause mutations most cancer causing chemicals carcinogens are mutagenic
Unit 6- Ch 6
EQ: What are restriction and enzymes and how do they work new paragraph
genetic engineering is the manipulation of genes for practical purposes using complementary base pairing of DNA paragraph
examples:
DNA cloning producing identical copies of DNA
plasmids circular bacterial DNA are inserted into other source foreign DNA resulting in recombinant DNA paragraph
how is this done?
bacterial restriction enzymes endonucleases cut DNA molecules at specific DNA sequences called restriction sites usually making many cuts and creating restriction fragments new paragraph
restriction enzymes break two kinds of bonds…
covalent bond through backbone
hydrogen bonds through base pairs
cut that leaves hydrogen bonds intact / blunt ends
Eco RI produces sticky ends some basis separated leaving either three or five overhang
recombinant DNA constructed using restriction enzymes new line
important in order to join two pieces of DNA together they have to be cut by the same restriction enzyme
why? otherwise sticky ends won't match and DNA can't bind together or
For step three: add DNA ligase to seal DNA back together
plasmid mapping
in order to use plasma to create recombinant plasmids need to find out
which restriction enzyme will cut particular plasmid
how many places of restriction enzyme will cut curtain plasmid
how far apart restriction sites are
Unit 6: Ch 7
EQ: What is CRISPR and what are its applications in science?
CRISPR- Clustered Regulatory Interspaced Short Palindromic Repeats
Technique that uses “CRISPR- associated protein 9” or Cas9, a nuclease that cuts double-stranded DNA molecules as directed by guide RNA that’s complementary to “target” gene
CRISPR- Cas9 system is used to cut target gene and then “knock it off” or repair it
(single-stranded RNA→ U,A,G,C)
Applications:
Correction of genetic defect that causes sickle-cell disease
Addressing global problem of insect-borne diseases
Altering genes in mosquitoes may prevent it from transmitting disease, also known as gene drive, be using CRISPR can rapidly
Ch 1: Intro to Natural Selection
EQ: How fast is the process of evolution?
Evolution is genetically considered to be a very slow process… over 1,000s or millions of years!
But can evolution happen quickly?
Studies are suggesting evolution can happen quicker than we realized… this is called microevolution
Contemporary microevolution is ongoing genetic changes in a population.
Ch 2:
EQ: What are the origins of theory of evolution?
Charles Darwin
In 1859, Darwin published On the Origin of Species, which focused biologists’ attention on the great diversity of organisms
What is evolution?
Darwin proposed “descent with modification” i.e. current species are descendants of ancestral species
today, we define evolution as the change in genetic makeup of a population over time due to natural selection
Conditions necessary for natural selection…
1) variation exists in a population- organisms w/ favorite phenotypes have improved chance of survival
2) competition- organisms in. a population compete w each other for limited resources (food, sexual partners, space/territory, nutrients, light for plants)
Adaptations- traits/behaviors that provide an advantage in a particular environment
fitness- ability of an organism to survive and produce fertile offspring
reproductive success- the production on of offspring (applies to individuals)- “winners” of evolution!
heritability- the ability to pass on adaptations to new generations
natural selection- are the traits of individuals w more reproductive success become more common in the population
what changed?…
rise of paleontology in the 17000s study of remains of past organisms (fossils) ,found in sedimentary rock layers (strata)
fossils were different compared to modern forms
boundary between strata represented catastrophic event that destroyed many species; new species replaced them
extinctions were common
other relation new proposals…
geologists James Hutton (1726-1797) and Charles Lyell (1797-1875) suggested that geological changes were very slow gradual processes… in other words, Earth is really old!
Jean-Baptiste de Lamarck (1744-1829)
Unit 7-Ch 3:
EQ: How does natural selection differ from artificial selection?
Natural selection- overtime, increase in frequency of individuals w favorite adaptations results in organisms becoming well suited for life in their environment (“fittest”)
Key features of natural selection…
1) individuals w favorite traits survive and reproduce at a higher rate than other individuals… resulting in increased frequency of these adaptations in given environment
2) when the environment changes, natural selection may result in adaptation to new conditions, sometimes giving rise to new species
3) populations, not individuals, evolve over time ***
4) natural selection can only increase or decrease heritable traits that differ among individuals in a population (only mutations create new differences)
5) the specific traits that are adaptive will vary from place to place and over time
artificial selection- humans modify other species over generations through selective breeding of individuals w desired traits
Unit 7- ch 4:
EQ: who were Hardy and Weinberg?
Factors of evolution:
pinky: shrink/small population
ring: nonrandom mating
middle: mutation
pointer: movement/gene flow
thumb: natural selection
Godfrey Hardy and Wilhelm Weinberg:
Hardy-Weinberg principle states that genetic variation in population remains constant from one generation to the next in the absence of disturbing factors
populations- group of individuals that live in the same area and inter breed, producing fertile offspring
gene pool- consists of all the alleles in population
allele frequency- how common an allele is in a population (usually expressed as a decimal/percentage)
Hardy-Weinberg equation: p2+2pq+q2= 1(decimal) (100%- percentage)
used to test whether population is evolving
genetic variation required for population to evolve, but does not guarantee that it will
allele frequency= p or q values
p+q=1
p- dominant allele
q- recessive allele
p2- homozygous dominant (AA)
2pq- heterozygous dominant (Aa)
p2- homozygous recessive (aa)
individuals/people/organisms/phenotypes= p2, q2, 2pq
***Hardy-Weinberg equation describes genetic makeup expected for population is not evolving at specific locus under the following conditions
large/growing pop
random mating
no natural selection
no movement/gene flow
no mutation
no genetic evolution= Hardy-Weinberg Equilibrium
Hardy-Weinberg Equilibrium p2+2pq+q2=1
need at least 2 generations to compare in order to determine equilibrium
Unit 7: Ch 5-
EQ: What are gene flow and genetic drift, and how do they relate to natural selection?
Gene flow (“pointer finger”)
movement of alleles among populations… alleles are transferred through movement of fertile individuals or gametes
high rates of gene flow can reduce genetic variation over time (diluted gene pool) OR improve adaptation to local conditions
Genetic drift (sudden change)
process where allele frequencies decrease suddenly from one generation to the next*
reduces genetic variation through loss of alleles, especially in small populations
the smaller a sample, the more likely that chance alone will cause deviation from a predicted result
Genetic Drift can lead to…
Founder effect occurs when a few individuals become isolated from a larger population
allele frequencies suddenly change… due to chance
Genetic Drift can be caused by:
Bottleneck effect can result from a drastic reduction in population size due to a sudden environmental change
if the population remains small, it may be further affected by genetic drift
** Summary of Effects of Genetic Drift
1) significant in small populations
2) can cause allele frequencies to change at random
3) lead to a loss of genetic variation within populations
4) cause harmful alleles to become fixed
gene flow and genetic drift both lead to natural selection
3 modes of natural selection (“thumb”)
1) directional selection occurs when conditions favor individuals at one end of the phenotypic range
2) disruptive selection occurs when conditions favor individuals at both extremes of the phenotypic range
3) stabilizing selection occurs when conditions favor intermediate variants and act against extreme phenotypes
Balancing selection- occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population
balancing selection could include:
heterozygous advantage (heterozygous have higher fitness)
frequency-dependent selection (fitness depends on frequency)
Why can’t natural selection produce perfect organisms?
1) selection can act only on existing variations
2) evolution is limited by historical constraints
3) adaptations are often compromises
4) chance, natural selection, and the environment
Unit 7: Ch 6-
EQ: what is the evidence for evolution? And what is Phylogeny?
4 types of evidence for evolution
1) direct observations
2) homology
3) biogeography
4) fossil record
1) direct observations
biologists have observed evolutionary change in thousands of studies, for example:
rock pocket mouse- fur color
Sticklebacks- pelvic spines
MRSA- antibiotic resistance
2) homology
similarity of structures resulting from common ancestry
Related species can have characteristics with underlying similarity that function differently
3) anatomical homologies
homologous structures are anatomical similarities that represent variations on a structural theme present in a common ancestor
Comparative embryology reveals anatomical homologies not visible in adult organisms
Vestigial structures are remnants of features that served important functions in an organism’s ancestors but serve no current purpose
Analogous traits arise when species independently adapt to similar environments in different locations, and can lead to convergent evolution, or the evolution of analogous features in distantly related groups
Molecular homologies (determine relatedness of DNA’s sequence)
similar genes, amino acids, proteins and other structures inherited from common ancestor
More similarities= more closely related
3) biogeography
scientific study of the geographic distribution of species
islands generally have many endemic species (found nowhere else in the world)… often closely related to species on the nearest mainland or neighboring island
4) fossil record
provides evidence that species have changes through time and many species have gone extinct and can reveal origins of new groups of organisms
*Intro to Taxonomy
Phylogeny- the evolutionary history of a species or groups of related species
Modern phylogeny
phylogeny is inferred from similarities in morphology, genetics and biochemistry
common ancestry will reflect evolutionary relationships (similarities likely to be more closely related)
Relationships are shown with general cladogram, or more specifically a phylogenetic tree
unit 7: ch 7:
EQ: how does phylogeny relate to cladistics?
Phylogenetic trees- branch lengths
can reflect the number of genetic changes in DNA sequence
Can represent chronological time determined from fossil record
Cladistics: classifying organisms by common descent
a clade is a monophyletic group (ancestor species and all descendants)
Paraphyletic group
include an ancestral species and some, but not all descendants
Polyphyletic group
include distinctly related species, but not their most recent common ancestor
Shared ancestral vs derived characters
a shared ancestral character is a trait that originated in an ancestor of a clade
A shared derived character is a new trait (or loss of a trait) unique to a particular group
Ingroup vs out group
An ingroup is the group of species being studied
An outgroup is a species or group of species closely related to but not part of the ingroup
Using characters to create a cladogram
Unit 7: Ch 8-
EQ: How does natural selection lead to new species, or elimination of species
FRQ= measure overall fitness of evolution is reproductive success
Natural selection: a closer look
natural selection results in adaptive radiation… over a very long time this can lead to the formation of a new species
speciation
process by which 1 species splits into 2 or more species through reproductive isolation
microevolution vs macroevolution
speciation creates conceptual bridge between microevolution (changes in allele frequency) and macroevolution (broad patterns of evolutionary change); also punctuated equilibrium suggests rapid episodes of speciation between long periods of little/no change
the term “species” includes morphology and physiology, biochemistry, and dna sequences
species= group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring
limitations of the species concept:
1) cannot be applied to fossisl or asexual organisms
2) emphasizes besence of gene flow between speices, but gene flow does sometimes occur between distinct species
Allopathic Speciation (geo barrier)
geographic barrier exists to prevent breeding and the barrier delends on the ability of a population to disperse
for example, canyon create barrier for small rodents but not birds, coyotes or trees pollen
Sympathies speciation (no geo)
occurs in populations living in same geographic area, but gene flow is reduced through other factors including:
polyploidy (extra sets of chromosomes and common in plants)
Habitat differentiation
Sexual selection
Mass extinction- disruptive changes to the global environment cause the rate of extinction to increase drastically, where large numbers of species become extinct worldwide
Current estimates suggest that 99% of all living organisms that have ever lived on Earth are now extinct
Extinction
Organisms cannot adapt quickly enough to rapid environmental changes like:
invasive species
Diseases
Natural disasters
New predators
Humans
Unit 7- Ch 9
EQ: what are the origins of life?
the first cells
earth formed 4.6 billion years ago
Oldest fossils are prokaryotes from ~3.5 billion yrs ago
single celled organisms in bacteria and archaea domains
Conditions of early Earth
early atmosphere had little oxygen, likely only water vapor and compounds released by volcanic eruptions. Water vapor condensed into oceans, and hydrogen escaped into space
Phase 1: abiotic synthesis
Atmospheric components were converted into monomers through variety of processes requiring some sort of catalyst
Miller-Urey experiment
In 1953, Stanley miller and Harold Urey showed experimentally that abiotic synthesis of organic molecules was possible in a reducing atmosphere
Phase 2: synthesis of macromolecules
next, small organic molecules polymerized to form larger molecules… monomers are known to bind to mineral particles, holding them in close proximity and allowing bonds to form
Phase 3: development of pre-cells (protocells)
Development of membrane by phospholipid molecules, which naturally arrange themselves into spherical shapes
Phase 4: formation of self-replicating molecules
first, genetic material was likely rna
Riboenzymes are rna molecules that can catalyze reatxtions
RNA world
copying errors (mutations) occasionally result in daughter molecules w improved replication… faster, more accurate self-replication would leave more descendant molecules resulting in an “rna world”
Ch 1: responses to the environment
EQ: why do animals do what they do?
The how and why of animal activity
Behavior is an action carried out by muscles under control of the nervous system
Ex: acquiring food, finding mates, maintaining homeostasis
Behavior is subject to natural selection, and can even influence evolution of animal anatomy
Ethology- study of animal behavior (Niko Tinbergen)
Behavior ecology- study of the ecological and evolutionary basis of animal behavior
Behavior examples:
Innate- fixed action patterns (sticklebacks) or imprinting (young geese)
Learned- learned behavior comes from watching other animals and from life experiences
Associative- classical conditioning (Pavlov’s dogs)
Altruistic- reduces fitness of individual but may increase fitness of population (naked mole rat)
Ch 2
EQ: how do we define ecology, and how do we determine the distribution of organisms?
Ecology- scientific study of interactions between organisms and environment
Organismal ecology- individual living thing… considers how its structure, physiology and behavior meet environmental challenges
Population ecology- group of individuals of the same species living in an area… considers factors affecting population size over time
Community ecology- groups of populations of different species in an area… considers how interactions between species affect community structure and organization
ecosystem ecology- community of organisms in an area AND the physical factors w which they interact… emphasizes energy flow and chemical cycling between organisms and the environment
Landscape (or seascape) ecology- mosaic of connected ecosystems… focuses on the factors controlling exchanges of energy, materials and organisms across multiple ecosystems
Global ecology-
considers all of biosphere (global ecosystems)… sum of entire planet’s ecosystems and landscapes
Examines influence of energy and materials on organisms across the biosphere
Distribution- how organisms are spread across a geographic area
Transplants
organisms intentionally or accidentally moved to areas where previously absent
Successful transplants indicate that the species’ potential range is larger than its actual range
Density- # of individuals per unit area or volume
Dispersion- movement of individuals (or gametes) away from area of origin or centers of high population, a subsequent density pattern of spacing among individuals
Extrapolation- can be used to estimate densities and total population sizes when impractical or impossible to count all individuals in a population
Ch 3
EQ: how do we calculate population growth?
Idealized vs realistic growth
unlimited growth occurs under ideal conditions; but in nature, growth is limited by various factors
Ecologists study growth in both idealized and realistic conditions
Frequency of an event, such as birth or death, can be calculated per person in a population to illustrate population growth
Per capita- a Latin term meaning “by head” that is often used in place of “per person” in statistical observances
Changes in population size
population growth rate can be expressed mathematically…
N/t= B - D And N/t= dN/dt
Where N is the change in population size, t is the time interval, B is the number of births, and D is the number of deaths in the population during the time interval
Change in population size = births + immigrants entering population - deaths - emigrants leaving population
Exponential growth
occurs under idealized conditions= food is abundant and all individuals reproduce at physiological capacity
under such conditions, population increases in size by a constant proportion at each instant in time
Exponential growth is represented by the equation
dN= change in population size
dt= change in time
N= population size
r max= maximum per capita growth rate of population
Exponential growth
dN/dt= r max N
Exponential Growth
population growing exponentially increases at a constant rate ( r )
Results in a J-shaped growth curve
Higher intrinsic rate would mean steer growth curve
Carrying capacity
exponential growth assumes unlimited resources- not realistic!!!
Carrying capacity (k) is maximum population size in a particular environment can support
As a population approaches carrying capacity, per capita birth rate will decrease or per capita death rate will increase
Logistic growth model
per capita rate of increase approaches zero as the population density approaches carrying capacity= (no growth)
Logistic growth can be mathematically represented using an equation
dN= change in population size
dt= change in time
N= population size
K= carrying capacity
r max= maximum per capita growth rate of population
Logistic growth
dN/dt= r max N( K-N/K)
Logistic growth results in a S-shaped curve when resources are limited
Logistic model and real populations
fits few real populations since some populations overshoot M before settling down row relatively stable density, or some populations fluctuate greatly and make it difficult to define K
“Trade-offs” and selection type
r- selection produces many offspring that grow rapidly due to lower probability of survival to maturity (little care from parents)
k-selection produces few offspring that have higher probability of survival to maturity (higher level of care from parents)
Population density and change
Density independent- birth/death rate does not change with population density
Density dependent- birth decreases with density, or death rate increases with density
Factors of …
density independent:
Flood, fire, pesticide, temperature/ climate change, destruction of habitat, drought
Density dependent:
Food shortage, competition for mates or habitat, increased predation, parasite/ infectious disease, introduction to invasive species, competition for water/ resources
Ch 4
EQ: how does earth’s climate affect the distribution of species?
Determining climate
long-term weather conditions for a particular location
Four major abiotic components of climate:
sunlight
Precipitation
Temperature
Wind
Biomes- major ecological associations that occupy broad geographic regions of land or water
Biomes disturbances
Environmental change could mean previously unfavorable random genetic mutation/ variation could become advantageous
Humans can create drastic habitat changes or introduce new species
Intentional/accidental introduction of invasive species could lead to increased competition and pre-existing species exploiting a new niche
Ch 5
EQ: how can interactions between organisms be classified, and how can we track the flow of energy?
Symbiosis- interaction between organisms living in proximity… organized as having positive (+), negative (-), or no effect (0) on the survival/reproduction of interacting individuals
Instances:
Competition (-/-)
Individuals of different species compete for resource(s) that limits survival/reproduction of each
Ex. Weeds compete w garden plants for nutrients and water
Exploitation (+/-)
One species benefit by feeding on (and thereby harming) another species
Ex. Predation, herbivory and parasitism
Mutualism (+/+)
Benefits members of both interacting species (sometimes one or both cannot survive w/o the other)
Ex. Clownfish and sea anemones
Commensalism (+/0)
Benefits individuals of one species w/o harming or helping individuals of the other species
Ex. Cows graze in fields and move insects out of grass where egrets can catch and eat them
Ecological niche- specific set of resources (biotic and abiotic) used by an organism
resource partitioning allows similar species to coexist if one or more significant differences in their niches
Trophies level- occupied position in food web
feeding relationships are key factors affecting community structure and dynamics
Food chain and food web
Arrow always points to stomach of animal
10% rule- 10% of energy is transferred from one trophicnlevel to the next level (1000 → 100)
Keystone species
exert strong control on a community by their pivotal ecological roles rather than relative abundance Ex. Yellowstone grey wolves regulate prey populations, enabling other species of plants and animals to flourish
Ecosystem engineers
cause physical changes in the environment that affect community structure Ex. Beaver dams can transform landscapes on a large scale
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“drive” allele through the population
