BIO320 Ecology Test

Define population.

a group that includes all the members of a species living in a certain area

Define gene pool.

the alleles of all of the genes from all organisms in a population

Define allele frequency.

the proportion of a certain kind of allele in a gene pool

Define evolution.

changes in allele frequencies in a population over time

What does the Hardy-Weinberg principle say?

a population is not evolving as long as it satisfies 5 given conditions, meaning that allele and genotype frequencies remain consistent

What are the 5 conditions under which the Hardy-Weinberg equilibrium true?

no mutations, no gene flow, large population, fully random mating, and no natural selection

What is the point of the HW equilibrium if its 5 conditions are never met?

if we know that a population is evolving, we can evaluate each of the conditions of the HW principle to determine where the change is occurring from (evolution means the equilibrium is NOT being maintained)

Where do all new alleles originate?

mutations

Do mutations occur so that environmental challenges can be overcome?

no, they occur randomly; natural selection acts on these mutations, changing allele frequencies to make a population as a whole better adapted for environmental challenges over time

How many mutations does a newborn human carry on average?

70-80

Why are mutations important?

mutations are what give rise to new alleles, which are the basis of genetic diversity in all species; without mutations, there would be no alleles, meaning no evolution

What are the 2 main sources of genetic variation in bacteria?

mutation and conjugation

What are the 3 main sources of genetic variation due to sexual reproduction?

crossing over in prophase I; law of segregation / chromosome lining up in metaphase I to produce unique gametic combination; fertilization of 2 gametes

What is gene flow?

changes in distribution of alleles across populations

How does gene flow occur in baboon troops?

juvenile male baboons leaving to find another troop; if high enough social status is reached, they can breed in that troop and add their alleles to the gene pool

How does gene flow occur in tree populations?

tree offspring spreading due to seeds / pollen dispersed by wind, water, and/or animals; germination in a new environment results in that tree’s alleles added to the new gene pool

What is genetic drift and when is it important?

changes in allele frequencies due to chance events that somehow only allow a random subset of the population to survive, such as through natural disaster

How is allele frequency affected in varying population sizes with genetic drift?

allele frequency is generally reduced by genetic drift, but this effect is more dramatic in smaller populations, where it is much more likely that a certain allele is either completely removed (0% frequency) or becomes the only allele in the gene pool (100% frequency)

What is a population bottle neck?

a chance event drastically reducing a gene pool

What is the founder effect?

when a small number of organisms separated from their original population reproduce to create a new population, which typically has less genetic diversity than the original and differing allele frequency due to the small sample size

What is the challenge for species with shrinking gene pools?

less genetic diversity means less resilience to new environment / reduced ability to adapt and survive for the population as a whole (loss of advantageous alleles very likely)

Examples of population bottleneck?

elephant seal nearly going extinct due to overhunting (or many other species, for that matter); also the saiga antelope, cheetahs in Zimbabwe, giraffes in Africa, and American bison slaughtered by colonists to destroy the way of life of Amerindians

Founder effect example?

higher frequency of the Ellis van-Creveld allele in the Amish people of Lancaster County, Pennsylvania, due to relatively high allele frequency in the small group of ancestors of the current population

What are the two types of non-random mating?

inbreeding and assortative mating; do NOT change allele frequency in a gene pool

What is inbreeding and why does it occur?

mating with close relatives due to limited mobility resulting in most offspring of a parent living and reproducing in the same place

What is assortative mating?

choosing a mate that looks more similar

What does natural selection act on?

the reproductive (not always survival) success of certain phenotypes (then impacting genotypes)

What is sexual selection and what is an example?

sexual selection is the selection that acts on certain traits that help an animal compete for a mate; male bighorn sheep rams fight to mate with the females, and they have a higher difference in reproductive success because the losers have difficulty finding a mate or may even die while fighting

What is directional selection and what is an example?

selection that favors a certain extreme value of a phenotype, moving the average phenotype towards that extreme over time; mammals evolving to develop thicker fur during ice ages and antibiotic resistance coming from the selection pressure of high antibiotic usage in farm animals and medical practice

What is stabilizing selection and what is an example?

selection that favors the average value of a phenotype, reducing the amount of extremes and decreasing phenotypic variability; favoring Aristelliger lizards of a medium body size since smaller lizards struggle with defending territory and larger lizards are more likely to be eaten by owls

What is disruptive selection and what is an example?

selection that favors the two extreme values of a phenotype, reducing the amount of organisms with the average value and splitting the population into 2 more clearly defined phenotype groups over time; black-bellied seedcrackers either having a large, stout beak for hard seeds or a small, pointy beak for small seeds since a medium beak leads to difficulty in eating both kinds of seeds

How are species defined?

species are defined as reproductively isolated groups that can only mate with each other to produce fertile offspring, meaning that they evolve independently too; this only applies to sexually reproducing organisms and for asexually reproducing organisms like bacteria, other definitions are created based on their genomic similarities and key structures/functions

What are the 5 premating isolation barriers?

geographic isolation, ecological isolation, temporal isolation, behavioral isolation, mechanical incompatibility

What are the 3 postmating isolation barriers?

gametic incompatibility, hybrid invariability, hybrid infertility

What is geographic isolation and what is an example?

populations cannot interbreed because they are too far apart; Kaibab and Abert’s squirrel living on north and south rims of Grand Canyon

What is ecological isolation and what is an example?

populations are close together but living in different habitats; white-crowned sparrows live in field and meadows while white-throated sparrows live in dense thickets, or fruit flies reproducing on hawthorne and apple trees in same area

What is temporal isolation and what is an example?

populations breeding during different seasons; Monterey pine releases pollen in early spring while Bishop pine releases pollen in summer, both in same area on California coast

What is behavioral isolation and what is an example?

courtship signals, behaviors, and colors specific to a species; male Raggiana bird having a unique plumage and arresting pose to court females of only his own species

What is mechanical incompatibility and what is an example?

physical differences in anatomy that prevent mating; left-hand vs. right-hand spiral shapes preventing snails from mating since their reproductive organs cannot match up

What is gametic incompatibility and what is an example?

sperm unable to fertilize egg; sea urchin sperm cells having a specific protein to bind with only sea urchin egg cells of their own species, fluids secreted in female reproductive tract killing off sperm cells of other species

What is hybrid inviability and what is an example?

hybrids unable to survive or reproduce after cross fertilization; offspring of leopard and wood frogs bred in captivity dying after only a few days

What is hybrid infertility and what is an example?

hybrids unable to reproduce and pass genetic information onto offspring, blocking gene flow between species (often because chromosomes don’t pair properly during meiosis, preventing gamete development); ligers and mules being sterile

What are the 2 requirements for speciation to occur and why is each necessary?

some form of isolation of populations so that they can evolve separately (geographic isolation is often a precursor for other barriers to develop); genetic divergence of populations so that there are other resulting isolating mechanisms, which may arise through genetic drift or natural selection for differing environments

What is allopatric speciation and what are the 3 ways it seems to happen?

new species forming due to the geographic separation of a population; may be because organisms colonize new isolated habitats, geological changes transforming the landscape, or climate shifts altering distribution of vegetation or parts of populations, like in ice ages

What is sympatric speciation and what are the 2 ways it seems to happen?

new species forming in the same geographic area (isolated in a way that is not geographic, stopping gene flow); may be due to ecological isolation, like the reproductive separation of fruit fly on apple trees and hawthorns, or genetic isolation, like the instantaneous creation of new species due to mutations resulting in polyploidy, especially self-fertilizing and/or asexually reproducing plants

What is adaptive radiation and what are some examples?

when populations of 1 species arrive in a variety of new habitats and evolve separately due to differing selection pressures rapidly enough that it seems they all evolved around the same time; examples are a Californian tarweed turning into 30 species of Hawaiian silverswords or 600 species of cichlids evolving in Lake Victoria in 12,000 years

What are the 4 factors that increase a species’ risk of going extinct?

localized distribution, specialization, introduced competition/predators, and habitat loss/change

Describe localized distribution and an example.

only being located in a very specific place; the Devil’s Hole pupfish found in only 1 spring-fed water hole in the Nevada desert

Describe specialization and an example.

being adapted to only a very specific environment; the Karner blue butterfly feeding only on the blue lupine or pandas only eating bamboo

Describe introduced competition and/or predators and an example.

not being adapted for the sudden introduction of species that are either competition or are predators; predatory brown tree snake introduced in Guam nearly wiped out all of the native birds

Describe habitat loss/change and an example.

destroying or changing various aspects of the habitat a species is adapted to; clearing tropical forests and melting ice caps are examples of habitat loss, while global warming damaging coral reefs and ticks feeding on moose slowly migrating north due to rising temperatures are examples of habitat change

Why did primates develop forward-facing eyes?

vision accuracy and depth perception due to overlapping fields, suitable for climbing from branch to branch high in the air due to their tree dwelling lifestyle

Why did primates develop color vision?

spotting ripe fruit (more 3 dimensional than smell)

Why did primates develop grasping hands?

holding onto branches and mother, eventually also grasping tools once bipedalism developed

Why did primates develop large brains?

rapid movement through trees, dexterity, supporting binocular vision, remembering food location, intelligence for social interaction in complex hierarchies

What was the first bipedal hominid and when did it evolve?

Ardipithecus ramidus - 4.4 million years ago

What evidence proves that A. ramidus was bipedal? How big were their brains?

knee joints allowing legs to fully straighten and hip joints providing vertical column of support + footprints almost 4 million years old found in Tanzania; brains were much smaller than modern humans but still larger than ancestors

How did tool technology change from 2.5 mya to 600,000 years ago?

became more complex; rocks chipped symmetrically to form double-edged tools and sharper blades formed with finer hand control allowing for tiny flakes to be chipped off stone (Neanderthals)

What was Neanderthal culture like?

physically and technologically similar to humans, but not as much of an advanced culture with our level of art, music, and rituals

What are the distinguishing features of modern humans?

tall skulls with high, domed craniums and vertical foreheads, narrow faces with small cheekbones and projecting chins, culture including beads, advanced stone tools, art, and language

What are the 6 trends in primate evolution?

clasping hands and feet + rotation elbow and shoulder joints for climbing; forward-facing eyes and reduced sense of smell due to tree life; hand-eye coordination for climbing and food gathering; small litters with long infant dependency periods to teach social and feeding behavior; large brain to body weight ratios and large cerebral cortex for learning, especially about social relationships; complex social behavior with facial expressions and different vocalizations

When did the earliest primates evolve?

50-55 million years ago

How old is the shared common ancestor of humans and chimps?

7 million years ago

What does the term hominin refer to?

species such as Australopithecines that were direct ancestors or close relatives to Homo sapiens

What are the 4 trends in human evolution?

bipedalism; greater manual dexterity (precision + power grip with shorter fingers than chimps); rounder dental arcade, reduced canines, and flattened molars for omnivorous diet; increasing brain size allowing for behavioral complexity and cultural development

What was the selection pressure of bipedalism in hominins?

more energy efficient than knuckle walking when traveling for food; hands free to carry food, babies, tools, etc.; upright posture allowing for better vision to see predators and follow prey

What was the selection pressure of increased cranial capacity in hominins despite the extra energy cost?

supporting binocular vision; rapid movement and dexterity for navigating trees; remembering food location; learning customs for social interaction

What are homologous structures and what is an example? How do they support evolution?

Body parts with similar internal anatomy but changes in current function and/or external appearance, such as similarly structured forelimbs for different functions like climbing, flying, running, and swimming; demonstrates that these organisms had a common ancestor from which the structures adapted to new environments (divergent evolution)

What are analogous structures and what is an example? How do they support evolution?

Body parts with similar function and/or external appearance but differences in internal anatomy adapted for similar environments, such as wings on birds, bees, and bats; demonstrates that organisms evolve based on similar selection pressure despite having a much older common ancestor (convergent evolution)

What are vestigial structures and what is an example? How do they support evolution?

Body parts that no longer serve the original purpose they were developed for, such as wisdom teeth in humans; they can be homologous to structures in other species and demonstrate common ancestors

How do embryological similarities such as the existence of tails and gill slits support evolution?

Indicates that different species develop similarly in the womb because of how their common ancestor developed, but differences and unique appearance at end of gestation shows evolutionary development since that ancestor

How does the remarkable similarity between cytochrome c in mice and in humans support evolution?

Both mice and humans need cytochrome c for the same purpose since the shared common ancestor had that gene, but some changes have occurred due to mutations passed on since that ancestor

What are the biochemical similarities shared by all living things and what do they prove?

DNA carrying genetic information, roughly same set of amino acids, ATP as cellular energy carrier, and RNA, ribosomes, and approximately same genetic code to translate DNA to proteins; these mechanisms are too specific and complex to have developed on their own, showing that all of these species have a common ancestor

Describe the Kaua’i calling cricket evolution. How long did this evolutionary response take? How intense was the selection pressure?

Male Kaua’i crickets creating loud calls used to have an advantage of attracting female mates, until parasitic flies spiked their mortality rate because they could find the louder males faster. As a result, calling males were rapidly selected against. It look less than 20 generations (1990s to 2003) for the evolutionary response to occur because of very intense selection pressure (significantly easier for the parasitic flies to find the calling crickets instead of the silent crickets).

Examples of resistance to herbicide and antibiotic

Plants becoming resistant to glyphosate (Roundup), Staphylococcus aureus becoming resistant to more antibiotics (MRSA); all occurring due to increased selection pressure as a result of human activity

Examples of evolution in a natural population

Anolis sagrei lizards developing short, thin legs for walking on thin-branched bushes and long, thick legs for outrunning predators on thick-branched trees depending on which of the 14 islands they were placed on (after 14 years); Finland tawny owls moving towards brown color due to climate change and less snow on the ground, easier to camouflage with dirt

How does human activity affect rates of evolution?

It rapidly speeds it up because we change environments dramatically through our activities, creating intense selection pressure

Where do new alleles come from?

Mutations

What does best adapted mean?

Organisms that have the highest chance of reproduction in their current environment