Ecology & Evolution Exam 2

Essentialism

variation observed was simply the imperfect copies of the ideal form of the essence (ideal is perfect and unchanging) (just imperfections in the individual)

Scala naturae (Great Chain of Being)

organisms are unchanging and range from simple to complex; no extinction, no new species, no variation; idea that developed before world exploration and discovery of fossils

principle of plentitude

- unchanging essence of all things in god's mind

- plentitude: god is perfect, so everything he created must be perfect, so no extinction (implies imperfection)

harmony of nature

- belief that nature is perfectly balanced and orderly because it was designed by god

- every species had a specific role

- the world had enough resources for all God's creations

Tycho Brahe

in 1572 he saw a new star in the sky, evidence constellations were not unchanging

Heliocentrism

Copernicus found the Earth moved around the sun

Galileo

discovered sun spots; craters on the moon

James Hutton

founded uniformitarianism, physical processes at present same as in the past (landforms produced by same physical processes)

Jean-Batiste de Lamarck

earliest uncompromising advocate of evolution

- internal forces: unknown internal mechanisms causes differences between parent and offspring

- inheritance of acquired traits: use or disuse of trait alters trait through lifetime, which is then passed to offspring

Charles Lyell

formed the principle of geology, changes in earth gradually accepted

Darwin's Voyage & Evolution Framework

- he was a naturalist on the Beagle

- he observed variation in the Finches and Rheas

What did Weismann discover?

- germ cells and somatic cells are different and heredity comes from germ cells

- environmentally acquired characteristics from parent is not passed to offspring (losing a leg)

What did Mendel discover?

- necessary mechanism of heredity (how traits are passed down)

- genes do not blend (black cat+white cat does not = grey kittens)

What were the Two Competing Schools of Thought (1900-1920's)

- mendelians

- biometricians

Biometricians

- continuous variation: traits are on a spectrum (height); gradual changes for evolving

- Weldon and Pearson

Medelians

- discontinuous variation: traits are in categories (gender); big jumps for evolving

- De Vries and Bateson

Reconciliation (Neo Darwinism)

- demonstrated natural selection could work on all observed variation and Mendel's laws, mendelian principles create biometrician results

- R.A. Fisher: "The Genetical Theory of Natural Selection"

- J.S.B. Haldane: "The Cause of Evolution"

- Sewall Wright

What completed "Modern Synthesis"

- Systematists: many small genetic changes over time can produce new species, Ernst Maye "Systematics and the Origin of Species"

- Paleontologists: fossil evidence supported population genetic mechanisms of neo-darwinism, George Gaylord Simpson "Tempo and mode of evolution"

Tree of Life

branches off into bacteria, archaea, & eukaryotes

DNA

• a molecule composed of two strands of nucleotides that are wound together into a double helix

• each nucleotide has 1 of 4 nitrogenous bases: (A, T, C, G), order of bases codes for genetic info

Chromosomes

compact structures consisting of long strands of DNA wound around proteins

Alleles

different forms of a particular gene

polygenic traits

: when a single trait is affected by several genes; enables phenotypes to span a range of values in a population (e.g., human body height).

Pleitropy

- when a single gene affects multiple traits

- The frizzle gene in chickens causes feathers to curl outward, but also causes other variations including faster metabolism, slower digestion, and less frequent egg laying

epistasis

- one gene masks or modifies the expression of another gene

- Mouse hair color is determined by a gene that codes for black or brown pigments. A second gene determines whether the hair will have any pigments at all

gene pool

all the alleles of every gene found in a population

Sources of Genetic Variation

- random assortment

- mutation

- recombination

Random Assortment

each gamete receives a random combination of alleles/chromosomes, could be any combination of those possessed by the diploid parent

Mutation

- a random change/typo in DNA nucleotide sequence

- can have no effect, alter physical appearance, or be lethal

- Some bacteria survive exposure to drugs and develop a mutation that makes them drug-resistant (MDR-TB) to antibacterial drugs curing tuberculosis

Recombination

- reshuffling of genes when chromosomes exchange DNA during crossing over

- can also occur between nonhomologous chromosomes

-helps immune system rapidly evolve

Mechanisms of evolution

- Mutation

- Migration

- Genetic Drift

- Natural selection

- Sexual selection or non-random mating

Mutation example

- in Seneca Army Depot of New York, many deer have white coats due to a mutation

- though detrimental hunting them is banned providing strong selection and white coats became common

Genetic Drift

- a process that occurs when genetic variation is lost due to random variation in mating, mortality, fecundity, and inheritance

- more common in small populations because random events can have a large effect on frequencies of genes

- mexican cavefish living in cave streams have smaller and less pigmentation than those in surface streams

Bottleneck effect

- type of genetic drift

- a reduction of genetic diversity in a population due to a large reduction in population size (e.g., from loss of food)

Founder effect

- type of genetic drift

- when a small number of individuals leave a large population to colonize a new area and bring with them only a small amount of genetic variation

- water hyacinth from South America has invaded many parts of the world, a single genotype dominates 75%, and 80% are composed of a single genotype

Requirements for natural selection

- variation among individuals:

- inheritance of variation:

- more offspring produced than survive:

- individuals with favorable characteristics more likely to survive and reproduce

- differences in fitness related to this variation-- selection

Hardy Weinberg Principle

- model used to see if a population is evolving by comparing expected and observed allele/genotype frequencies

- null hypothesis: assumes no evolution

- gene pool: all copies of all alleles in a population

Assumptions of HWP

- No migration

- No mutation

- No selection (no allele has higher fitness)

- Random mating

- Large population size

• Also assumes—diploid organisms, sexual reproduction, diallelic trait(only 2 allele traits)

HWP equations

- 1=p2+2pq+q2

- 1=p+q

(numbers come from punnett squares)

Selection

some individuals survive/reproduce better

Fitness

genetic contribution to next generation

Relative fitness

fitness compared to other individuals

Directional selection

- favors one extreme, mean changes, variation is stable

- when individuals with extreme phenotypes experience higher fitness than the average population phenotype

- Drought on the Gálapagos Islands increased the proportion of large seeds. Birds with large beaks were better able to consume large seeds, so large beaks were selected for

Stabilizing selection

- favors mean value, mean stays the same, variance decreases

Disruptive Selection

- favors both extremes, mean does not change, variance increases

- when individuals with either extreme phenotype experience higher fitness than individuals with an intermediate phenotype

- Mexican spadefoot toad can have mouth morphology to be carnivorous, omnivorous, or an intermediate consumer. Individuals with intermediate morphology are not well-suited for any particular resource type and are selected against

Microevolution

- the evolution of populations; affected by random processes and selection

- artificial selection

- natural selection: favors trait combinations that provide higher fitness to an individual, an ecological process; individuals interact with their environment, and traits that lead to greater fitness in an environment are passed on. Fish prefer to consume large prey (e.g., amphipods). Hence, small prey size is selected for.

Industrial melanism

- a phenomenon in which industrial activities cause habitats to become darker due to pollution; individuals possessing darker phenotypes are favored by selection

- peppered moths

Macroevolution

evolution at higher levels of organization including species, genera, families, orders, and phyla

Speciation

- macroevolution

- the evolution of new species

Phylogenetic trees

- macroevolution

- hypothesized patterns of relatedness among different groups such as populations, species, or genera; depict which groups evolved from other groups

- Scientists work from the premise that species with the greatest number of traits in common are the most closely related (e.g., shape and structure of fossils, DNA).

Allopatric speciation

- macroevolution

- the evolution of new species through the process of geographic isolation

- occurs when a single population is separated by geographic event, isolated populations experience genetic drift and founder effects so populations evolve separately. Populations become so different they cannot interbreed and evolve into new species

- Darwins Finches

Sympatric speciation

- the evolution of new species without geographic isolation

- Cichlids in Lake Tanganyika have evolved into 200 unique species from a single common ancestor, species have been facilitated by presence of distinct habitats through the lake

Polyploid

- speciation

- a species that contains three or more sets of chromosomes; can also give rise to sympatric speciation

- arise when homologous chromosomes fail to separate during meiosis, producing diploid gametes

- unable to breed with diploid and is genetically distinct from parents

- a blue-spotted salamander experienced incomplete meiosis and mated with a Jefferson's salamander which created a new triploid, all-female species, known as Tremblay's salamander

exposing plants to cold temps at time of reproduction increases chance of plants producing diploid gametes

- Polyploid plants tend to produce larger flowers and fruits.

- Many anthropogenically cultured flowers and fruits are polyploids (e.g., wheat

Evolution key innovations

- The evolution of winged mammals (e.g., bats), enabled them to catch flying insects and collect nectar from flowers.

- The evolution of C4 and CAM photosynthesis allowed flowering plants to grow in regions with scarce water.

- Selection on wing morphology among treehoppers produced distinctive horns that serve a wide variety of functions, such as defense, mating, and camouflage.

Adaptations to water density

- Some body tissues are more dense than water (e.g., bone); some are less dense

- Organisms have developed many adaptations to cope with their tendencies to sink or float

- many fish have gas-filled swim bladders that can equalize their density with surrounding water

- some algae use droplets of oil as flotation devices

Adaptations to water viscosity

- viscosity: thickness of a fluid that causes objects to encounter resistance as they move through it

- waters viscosity is high

- streamlined bodies reduce drag

- tiny marine animals rely on drag for movement, evolved long, filamentous appendages

Thermal properties of water

Water is resistant to changing states; helps prevent bodies of water from freezing solid during winter

Adaptations to water depth

- Hydrothermal vents release plumes of hot water with high concentrations of sulfur compounds and other minerals.

- tubeworms live around the vents & possess specialized organs that gouse vast numbers of chemosynthetic bacteria that live in a close relationship with tubeworms

- tubeworms capture sulfide gases and CO2 from surrounding water and pass these compounds to the bacteria, bacteria then use sulfide gases and CO2 to produce organic compounds, some are passed to the tubeworms

Osmoregulation

mechanisms organisms use to maintain a proper solute balance

Salt balance in aquatic animals

- sharks convert ammonia into urea, most urea is excreted but some retain in the bloodstream

- this raises the osmotic potential of their blood to seawater, which balances water movement

Salt balance in plants

Mangrove trees on mudflats maintain high concentrations of organic solutes in their roots to increase osmotic potential and secrete salt from leaves

Freshwater salinization

the increased concentration of salt in rivers, streams, lakes, and wetlands

Effect of Salt Concentration on Amphibians

sample of ponds in Adirondack Mountains of NY, ponds closer to roads had higher conductivity (salt) so spotted salamanders snd wood frogs declined in survival

Diffusion of carbon dioxide for aquatic plants

- CO2 diffuses slowly through water so they use bicarbonate bicarbonate (HCO3-) or carbonate (CO3-) ions for photosynthesis

Diffusion of oxygen for aquatic plants

- Not a problem for aquatic organisms that rise to the surface to obtain O2 from the air

- organisms obtaining O2 from water may be metabolically limited by low solubility and diffusion, particularly in waters that do not support photosynthesis

Countercurrent circulation

- adaptation where blood and water flow in opposite directions so concentration of O2 in water is always greater than concentration in blood

- helps to conserve heat by positioning arteries that carry warm blood away from the heart alongside veins that carry chilled blood from the extremities back to the heart

Diffusion of oxygen examples

- deep ocean organisms have low activity rates, reduces O2 demand

- zooplankton can increase the amount of hemoglobin in their bodies, stores more O2

- spotted salamander eggs have mutualistic relationship with algae, eggs provide CO2 to algae and algae provide O2 to eggs

Photosynthesizing Animal

Sea slugs can accumulate chloroplasts in their bodies from the algae they eat. These chloroplasts produce sugars that are used by the slug

Anaerobic (anoxic) environment

- completely devoid of oxygen

- some plants extend their roots above soil to absorb O2 from air

- many microbes use other sources of metabolic energy

Heat constraints for molecules

- proteins & other molecules become less stable, not function properly, and denature

- fats become fluid with heat, stiff with cold

- some bacteria are thermophilic (heat-loving) and live at temps up to 110°C

- thermal pollution: changing temp of environment via human discharges

Cold constraints for molecules

- crystal structure of ice can damage living cells

- marine vertebrates can freeze, added solutes in seawater lower freezing point, freezing point of water in animals is higher

- glycerol & glycoproteins

glycerol & glycoproteins

chemicals present in some animals that prevent freezing by reducing strength of hydrogen bonds or via supercooling

Thermal optima

- the range of temperatures in which an organism best performs

- determined by properties of an organism that influence ability to function (enzymes, structure of cells and tissues)

- fish species in cold waters swim actively and consume oxygen at rates comparable to fish near equator

Isozymes

- different forms of an enzyme that catalyze a reaction

- two or more isozymes suited for different temp ranges, useful for organisms that must cope with variable temps

- rainbow trout live in in streams with cold winters and warm summers, they produce a winter enzyme with high enzyme-substrate affinity, and a summer enzyme

Temperatures that exceed thermal optima

- can be detrimental

- coral bleaching, can occur if summer temps are just 1°C higher than average

Soil nutrients

- plants need O, C, H, and inorganic nutrients (N, P, Ca, & K) for survival and growth

- N, P, Ca, & K make proteins, nucleic acids, ect.

- nutrients (ammonium, nitrate, phosphate, calcium, and potassium) dissolved as ions in water held by soil

Cohesion

mutual attraction of water molecules; allows water to move up through empty remains of xylem cells

Root pressure

when osmotic potential in the roots of a plant draws in water from the soil and forces it into xylem; can raise water to ~20 m

Transpiration

the process by which leaves can generate water potential as water evaporates from the surfaces of leaf cells

Cohesion-tension theory

the mechanism of water movement from roots to leaves due to water cohesion and water tension

Stomata

- small openings on leaf surfaces that are points of entry for CO2 and exit points for water vapor; bordered by guard cells that open and close each stoma

- stops excess transpiration so plants don't wilt

electromagnetic radiation

- energy from the Sun; packaged in small, particle-like units called photons

- Photon energy is positively related to frequency and inversely related to wavelength

Photosynthetically active region

wavelengths of light that are suitable for photosynthesis; includes wavelengths from 400 nm (violet) to 700 nm (red)

Chloroplasts

specialized cell organelles found in eukaryotic photosynthetic organisms

What substance(s) absorbs light?

- Chlorophylls (primarily a) and carotenoids are pigments inside the thylakoids

- Chlorophylls absorb red and violet light, and reflect green and blue light

- Carotenoids reflect orange and red light; allow plants to absorb a wider range of solar energy

Photosynthesis

- process of combining CO2, H2O, and solar energy to produce glucose (C6H12O6)

- 6 CO2 + 6 H2O + photons --> C6H12O6 + 6 O2

Where does the Calvin cycle take place?

stroma of the chloroplast

What does the calvin cycle do?

energy in ATP and NADPH is used to convert CO2 into glucose

Types of Calvin cycles

- C3: most plants (common, Rubisco, inefficient)

- C4: grasses, sedges (derived, Pep and OAA, reactions physically separated)

- CAM: family crassulaceae (derived, Pep and OAA, temporal separation of reactions)

C3 Photosynthesis

- CO2 + RuBP --> 2G3P

- RuBP: ribulose biphosphate; five-carbon sugar

- G3P: glyceraldehyde 3-phosphate; three-carbon sugar

- Process is catalyzed by RuBP carboxylase-oxidase (also known as Rubisco).

Disadvantage of C3 Photosynthesis

- Rubisco is inefficient

- Low affinity for CO2, so plants need large amounts

- Rubisco also preferentially binds to O2.

- Hence, C3 photosynthesis is not optimal in very hot and dry conditions

C4 photosynthesis

- a photosynthetic pathway in which CO2 is initially assimilated into a four-carbon compound, oxaloacetic acid (OAA); provides an advantage in hot and dry conditions

- CO2 + PEP --> OAA

- PEP: phosphoenol pyruvate; has higher CO2 affinity than Rubisco

- Calvin cycle occurs in internal bundle sheath cells; after OAA is converted to malic acid

- CO2 concentrations in sheath cells are 3-8 times higher than is available in C3 photosynthesis

CAM photosynthesis

- a pathway in which the initial assimilation of carbon into OAA occurs at night

- Instead of separating the steps of CO2 assimilation between mesophyll and bundle sheath cells, the steps are separated in time

- During days, stomata close to reduce transpiration rates

- Stomata open to exchange gases during the night, when cool temperatures slow transpiration

- C3 plants are adapted to cool, wet conditions

Root structural adaptations

- Shallow roots are able to take up water after brief rainfall events

- Long roots can access deeper waters

Other structural adaptations

- Resins and waxy cuticles protect plants from direct sunlight and slow water loss

- Spines and hairs provide protection and produce a boundary layer of still air that traps moisture and reduces evaporation

- Small leaves with a high density of veins prevent loss of leaf tissue via embolisms, or air bubbles in veins, which are common in water-stressed environments

Homeostasis

an organism's ability to maintain constant internal conditions in the face of a varying external environment

Negative feedbacks

- The action of internal response mechanisms that restores a system to a desired state, or set point, when the system deviates from that state

- hypothalamus triggers increased metabolism when body temp is below 37°C, and sweating when above 37°C

Water and salt balance in animals

- Terrestrial animals, with internalized gas exchange surfaces, are less vulnerable to respiratory water loss than plants.

- Organisms must exhibit behavior to acquire or remove solutes to maintain the proper concentrations of water and solutes.

- Animals acquire mineral ions in the water and food they consume. Water intake and urine excretion eliminate excess salts.

- When water is scarce, animals exhibit numerous adaptations.

Water and salt balance in animals examples

- desert kangaroo rat conserves water by hunting at night and staying below ground in the day, larger kidneys permit increased water retention

- organisms with no access to freshwater eliminate slat in their drinking water through specialized salt-secreting organs

Nitrogen balance in animals

- most aquatic animals eliminate excess nitrogen as ammonia

- many terrestrial animals produce metabolic by-products that can accumulate in higher concentrations (mammals produce urea and birds/reptiles produce uric acid)

- these compounds conserves water needed to remove excess nitrogen, but are energetically costly to make