Biology Test 1
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- *Generic: Development or change over time
- *Biology: change in the gene pool (heritable traits) that occur over time/generations due to selection pressures-
Breeding: Dogs, Crops/flowers, horses
-Favorable phenotypic characteristics appear, allow population to survive
- Study of genetic composition, or the allele frequency of a population.
- Modern synthesis= (evol. Bio)+(pop. genetics)
physical expression of a gene
features of a phenotype
specific form /value of a character
characteristic traits partly determined by genes
genetic makeup of an individual
Hardy Weinberg 5 requirements
- -Mating is random 0 Population size is infinite (or at least very large)
- -Large populations aren’t affected by genetic drift (random fluctuation in allele frequency)
- -No gene flow—no migration into/out of the population
- -No mutation
- -Natural selection does not affect survival of any genotypes
- -Believed in predictability of genotypic frequencies.
- -Mutations (good or bad, could go back)
- -Gene Flow (in and out, migration)
- -Nonrandom mating (mate selection)
- -Natural selection
- *Acts on the phenotype
- *Increases frequency of the allele 0 *Testament to the fitness of the individual
Natural selection can ______ a population
- Stabilize- preserves average characteristics
- Directional- favors charact. at on extreme
- Disruptive- favos charact. diff. from average
- Favors characters that enhance sex succes
- -ornate peacock feathers... recessive
Constraints of evolution
- Limitations to adaptations
- -Must observe laws of physics
- -Step-wise modifications of pre-existing models.
- -Some adaptations are beneficial but too costly or maladaptive and can be removed overtime
All biotic and abiotic within a defined boundry
Earth differs from other plantes in that
- Earth has lithospheric plates, liquid water,
- Atmosphere, moderate surface temperature, living organisms
Recycled Components of ecosystem
Nitrogen, oxygen, sulfur
Four Physical environment compartments
- Lowest layer of the atmosphere and contains
- 80 percent of the mass (water vapors + other gases)
Most air circulation
Extends out to about 50 km. Most materials enter the stratosphere from the region of troposphere that encircles the equator
- Holds moisture
- Warms the surface through heat retention
- Ozone layer blocks out harmful solar UV rays
- Ozone Layer has been depleted
- UV radiation= skin cancer, cataract formation, and crop damage
- H2O, CO2, methane, etc.
- -Transparent to sunlight but trap heat from surface
- - Exchange materials with the atmosphere only at their surface, receive material from land and run-off
- -Mix Slowly
- Where offshore winds push water away from shore
- Cold bottom water that moves up to replace it is nutrient-rich and supports high rates of phytoplankton productivity, which supports large consumer populations (aka Fish)
Fresh Waters Compartment
- Lakes, Rivers, and groundwater(soil&rocks)
- Water moves rapidly through this compartment.
- Mineral nutrients enter fresh waters through weathering of rock, and are carried to lakes and oceans
- Spring and Fall
- -Warm top cold bottom, help of wind
Elements move slowly on land. Runoff can bring minerals from land, rocks to oceans.
Connected to the atmospheric compartment by organisms that remove elements from the atmosphere, and also release elements to the atmosphere.
Net primary production
Humans consume ___ of Earths net primary production
Store pools of groundwater
All organisms contain carbon and their energy comes from carbon compounds
- Carbon is removed from the atmosphere as 14,12 CO2 and incorporated into organic molecules by photosynthesis—Carbon fixation
- Carbon fixation requires a source of energy such as sunlight, and an electron donor i.e., water.
Organisms that grow by fixing carbon, producers
Grow by using the already fixed carbon
Carbon is returned to the atmosphere by___.
- *by consumers (metabolism)
- *Biomass burning-- accounts for 40% of Earth’s production of CO2
- *Fires consume the energy stored in plant tissues and release the chemical elements (eg., CO2)
- -lightening -arson -management of vegetation
A group of organisms that can successfully mate with one another.
Share many alleles, genetic traits
Morphological Species concept
Carolus Linnaeus "species look alike"
Look alike but do not inderbreed
Lineage Species Concept
Species as branches on the tree of life
Splits two branches in Phylo Tree
When two populations can no longer exchange genes; speciation
Biological species concept
A species is defined as a group of actually or potentially interbreeding populations.
Occurs when populations are separated by a physical barrier
- Partition of a gene pool without physical isolation.
- Can occur with disruptive selection.
Prezygotic reproductive barriers
Before fertilization to prevent mating
- • Habitat isolation
- • Temporal isolation—mating periods do not overlap
- • Mechanical isolation—differences in size and shape of reproductive organs makes mating impossible
- • Behavioral isolation—e.g, frogs reject mating calls from very closely related species
- • Gametic isolation—eggs of one species don’t have appropriate chemical signals for sperm of another species;
Postzygotic reproductive barriers
- Act after fertilization to prevent the development of viable offspring, or their fertility.
- • Low hybrid zygote viability—zygotes fail to mature or have severe abnormalities –cannot develop
- • Low hybrid adult viability—offspring have lower survival rates –unlikely to reproduce
- • Hybrid infertility—offspring are healthy, but infertile e.g., mules, liger
- May develop in the absence of prezygotic barriers
- Contain individuals resulting from many generations of hybridization.
What drives speciation?
- Diet, dietary shifts: herbivores are much more numerous in species numbers than predators
- • Decreased dispersal ability; isolation • Mechanism complexity of mate selection
“selection” or “discrimination”= prezygotic barrier
The proliferation of a large number of species from a single ancestor
- If evolutionary rad. species live in a wide array of environments.
- -Hawaiian Islands
- -Pleistocene was a time of drastic cooling and climate fluctuation.
- -During four major and 20 minor “ice ages,”
- - Glaciers 15,000 years ago.
- -The time of hominid evolution and radiation.
- -Many large mammal species became extinct
- Climate was hot and humid but cooled and dried out half way through.
- Many flowering plants evolved and grasslands spread.
- Snakes lizards birds and mammals underwent extensive radiations.
- Crossed in 3 waves of mammals from Asia
- -1st time Rodents, marsupials, primates, hoofed mammals
- Continents resembled todays
- Extensive radiation of mammals
- Flowering plants came to dominate forests
- Mutations in one group of plants, legumes,
- allowed them to form symbiotic associations with N-fixing bacteria.
- This dramatically increased N available for terrestrial plants, and is fundamental to the ecological base of life today
- 145- 65mya
- Sea encircled tropics. Warm and Humid
- Dinosaurs cont. to diversify, snakes appeared
- Flowering plants began the radiation.
- Many mammal groups evolved
- Another mass extinction at end by meteorite
- On land, all animals larger than 25 kg became extinct
- Pangaea divided into Laurasia, drifted north; and
- Gondwana drifted south
- Ray-finned fishes began a great radiation.
- First lizards and flying reptiles (pterosaurs) appeared; most large terrestrial animals were dinosaurs
- Several groups of mammals first appeared Flowering plants appeared late in this period.
- First period of Mesozoic Era
- Pangaea began to break apart. On land, seed plants became dominant.
- A great radiation of reptiles began, which gave rise to crocodilians, dinosaurs, and birds.
- A mass extinction at the end eliminated about 65 percent of species.
- A relatively uninhabited world.
- The continents drifted apart, sea levels rose, and flooded the continents forming large shallow seas.
- Three groups of phytoplankton became ecologically important: Dinoflagellates, coccolithophores, and diatoms. Their remains form todays oil deposits.
- Continents came together to form the
- supercontinent Pangaea. By the end of the period, the reptiles split from
- a second amniote lineage- which leads to mammals
- Ray-finned fishes became common in fresh waters
- 1.At end of Permian, massive volcanic eruptions
- poured lava over large areas of Earth.
- 2.Volcanic ash and gases blocked sunlight and caused climate cooling, resulting in largest glaciers in Earth’s history.
- 3.[O2] dropped to 15%.
- - greatest mass extinction. ~ 96% of all species became extinct.
- Large glaciers formed over high latitudes but great swamp forests of horsetails and tree ferns grew on the tropical continents.
- These swamp plants became fossilized as coal.
- Diversity of terrestrial animals increased. Snails, centipedes, scorpions, and insects were abundant.
- Insects evolved wings. Flight gave them access to tall plants.
- Plant fossils show evidence of chewing by insect herbivores.
- Amphibians became larger; their lineage split
- from the amniotes— vertebrates with well- protected eggs that can be laid in dry places.
- In the oceans, crinoids reached their greatest diversity.
- There were evolutionary radiations of
- corals and squid-like cephalopods Jawed fishes replaced jawless forms
- Club mosses, horsetails, and tree ferns became common; some became tree size; the first soils developed.
- The first seed plants appeared, along with the first known fossils of centipedes, spiders, mites, and insects.
- Fish-like amphibians began to occupy land.
- End of Devonian: Mass extinction (~75%) of
- marine species.
- Two meteorite impacts may have contributed to this extinction. The craters evidence in Nevada, Western Australia.
- Marine life rebounded from the late
- Ordovician extinction.
- The first vascular plants, as well as some terrestrial arthropods (scorpions and millipedes) appeared in the late Silurian
- A great radiation of marine organisms;
- especially brachiopods and mollusks.
- At the end of the period, massive glaciers formed over Gondwana, sea levels decreased;mass extinction
- Beginning of the Paleozoic era.
- O2 concentration was increasing and the continents formed large land masses.
- Rapid diversification of life-- Cambrian explosion.
- Most of the major groups of animals living today (including extinct ones) appeared in the Cambrian period.
- For most of this era, life consisted of
- microscopic prokaryotes living in oceans.
- Eukaryotes evolved about two-thirds of the way through the Precambrian.
- By the late Precambrian; many kinds of multicellular soft-bodied animals evolved.
- most organisms can’t use N in this form.Nitrogen is an essential nutrient for DNA, RNA, ATP
- *Some bacteria convert atmospheric N2 into a form usable by plants
- *Industrial fixation– production of fertilizers *burning fossil fuels (generates N2O) *lightening
- It is lost rapidly from ecosystems-- vaporization (ammonia), denitrification
Effects of increased N fixation
- Excess fertilizers (N not taken up by crops) moves into groundwater or runoff and ends up in rivers, lakes, and oceans-- Eutrophication
- -“dead zone” (e.g, run-off in the Mississippi River watershed Gulf of Mexico) High Nitrogen levels promote algal growth; when these organisms die, their decomposition by microbes uses up the oxygen in the water.
- The resulting anaerobic/hypoxic conditions kill most other marine organisms.
- Hypoxia can reduce reproduction, levels of hormone, organ size, change gene expression level
- Increased atmospheric N2O, a greenhouse gas
- N2O also contributes to the formation of smog and tropospheric ozone (bad ozone).
- -global warming
Climate impacts on dead zones
- *In spring, 1. rainfall increases, more nutrient-rich
- water flows down the mouth of the
- Mississippi River- runoffs + 2. increasing temperature/sunlight
- algal growth in dead zones
- *In fall months, tropical storms enter the Gulf of Mexico and break up dead zones....
- cycle repeats next spring.
- Emissions of SO2 and H2S from volcanoes and fumaroles are the nonmicrobial sources of S in the atmosphere
- Microbial decomposition in marine and terrestrial environments returns S to the atmosphere.
- Many marine phytoplankton produce a sulfur compound that is broken down to dimethyl
- sulfide (CH3SCH3)major gas from ocean, ocean smell
- Dimethyl sulfide in the atmosphere forms particles around which water vapor condenses, forming clouds.
- Burning fossil fuels contributes SO2 to the atmosphere, where it can form sulfuric acid (H2SO4).
- Sulfuric and nitric acid (HNO3) form acid precipitation.
- Precipitation with pH less than 3.5 causes damage to plants. Acidification of lakes in the Adirondacks has reduced fish and aquatic insect species richness.
- *Phosphorus is an essential nutrient for DNA, RNA, ATP, and phospholipids.
- *Lacks a gaseous phase. There is very little in the atmosphere (dust)
- *Phosphorus cycles rapidly in organisms, but very slowly in Earth’s crust
- -Laundry detergents were formulated with sodium tripolyphosphate (STPP)
- Phosphorus is used to make artificial fertilizers
- Animal (human) wastes are high in P
- P is now accumulating, especially in agricultural soils.
- Excess P moves into surface waters – river, lake, ocean, streams
- Excess P entering lakes and rivers can cause eutrophication
- --stimulates the growth of algae. When the algae die, their decomposition by microbes consumes all of the oxygen in the lake
- Anaerobic organisms then dominate the bottom sediments
- Hypoxic conditions
- the full set of genes (coding and non- coding)
- For most organisms, DNA; some viruses, RNA.
- In eukaryotes, most of genes are in chromosomes, but some genes in chloroplast, mitochondria.
- • Study of the mechanisms and consequences of the evolution of macromolecules
- • Using molecular variation to reconstruct evolutionary history
Genes can evolve by
nucleotide substitutions, which can result in amino acid replacements
- -Change in the amino acid sequence alters the primary structure, which can then alter the secondary and tertiary structures of a protein.
- change the charge and structure can change its function.
Sequence alignment technique
Deletions and insertions in the sequence that have occurred since the two species diverged are determined by aligning sequences.
Sequence comparison can underestimate number of actual substitutions at that spot
- Multiple substitutions— more than one change at a given position
- • Coincident substitutions— different substitutions in different descendants
- • Parallel substitutions— same substitution in different descendants
- • Back substitutions—
- one change at a position is changed back to the original (reversions)
Sequence comparison can underestimate number of actual substitutions at that spot
To correct for underestimation, mathematical models are developed that describe how DNA and protein sequences evolve.
For example, transitions (changes between two purines or two pyrimidines) are more frequent than transversions (change between a purine and a pyrimidine).
- essential component of the electron transport chain of mitochondria
- • highly conserved protein
- across species (found in plants, animals, and many unicellular
- organisms) and its small size makes it ideal for studying biodiversity
synonymous (silent) substitution.
A substitution that does not change the amino acid sequenc
redundancy of genetic code
Many nucleotide substitutions have no effect on phenotype because most amino acids are specified by more than one codon-- *64 possible combinations ~> 20AAs (stop codons) bc codon read in triplets
nonsynonymous substitution (or missense substitution)
- A substitution that causes a change in the amino acid
- These are likely to be deleterious; but protein shape and function is not always altered, so it may be selectively neutral.
- e.g, substitution of GAG to GTG ~> Glu Valine; Sickle cell anemia
- This is usually the result of major errors during DNA synthesis.
- 3. Copies may have one of four fates:
- 1. retain original function (more product made)
- 2. retain original function but expression diverges in different tissues or at different times
- 3. becomes nonfunctional dt mutations/substitutions and becomes a pseudogene
- 4. accumulate substitutions that allow it to perform a new function
- -Vertical- inherited from ancestor
- – Lateral- from another organism
- • Horizontal/lateral gene transfer is highly significant amongst single-celled organisms.
- • Bacteria acquire characterstics from neighboring bacteria (antibacterial resistance)
- • Artificial horizontal gene transfer is a form of genetic engineering.
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