Feralis Ch 6 Flashcards
Microevolution
the changes in allele frequencies that occur over time within a population due to mutation, selection, gene flow, gene drift, and nonrandom mating
Macroevolution
the patterns of changes in groups of related species over broad periods of geologic time. Patterns determine phylogeny (evolutionary relationships among species and groups of species). These patterns can be used to establish a phylogenetic tree.
Lamarck Theory
Use and disuse - body parts can develop with increased usage and unused parts are weakened.
Inheritance of acquired characteristics - body features acquired during one’s lifetime can be passed down to offspring.
Natural transformation of species - organisms produce offspring with changes, transforming each later generation to be slightly more complex. Lamarck did not believe in extinction or the splitting of creating more species. This is an incorrect idea!
Darwin’s Theory - Natural selection
Survival of the fittest without any luck. Allele frequencies increase or decrease in order to adapt to the environment.
Darwin’s Theory - Descent with modification
Coined by Darwin, this occurs via natural selection. Over time and generations, traits providing reproductive advantage become more common within the population.
Neo-Darwinism
Synthetic theory of evolution that combines Darwin’s theory with the influence of genetics that Darwin was unaware of to propose mechanisms responsible for evolutionary patterns.
Evidence for Evolution - Paleontology
fossils reveal prehistoric existence of extinct species, and are often found in sediment layers. Deepest fossils represent the oldest specimens. Large, rapid changes produce new species.
Evidence for Evolution - Fossil types
actual remains, petrification, imprints, molds, and casts.
Evidence for Evolution - Biogeography
The geography that describes the distribution of species. Unrelated species in different regions of the world look alike when found in a similar environment. The supercontinent Pangea slowly broke apart to 7 continents due to continental drift.
Evidence for Evolution - Embryology
similar stages of development among related species establishes evolutionary relationships. Gill slits and tails are found in fish, chickens, pigs, and human embryos.
Ontogeny
The development of an organism.
Phylogeny
The evolutionary development and diversification of a species.
Evidence for Evolution - Comparative anatomy
this describes two kind of structures that contribute to the identification of an evolutionary relationship.
- Homologous structures
- Analogous structures
Evidence for Evolution - Comparative anatomy - Homologous structures
body parts that resemble one another between different species that descended from a common ancestor. E.g. bat wings vs. bird wings
Evidence for Evolution - Comparative anatomy - Analogous structures
body parts that resemble one another between different species that evolved independently. They have similar structures as adaptations to similar environments. These structures are also called homoplasies. E.g. bat/bird wings vs. bee wings
Evidence for Evolution - Molecular biology
this field examines nucleotide and amino acid sequences of DNA and proteins from different species. More than 98% of nucleotide sequences in humans and chimpanzees are identical. Amino acids in the protein cytochrome c are often compared.
Evidence for Evolution - Comparative biochemistry
organisms with a common ancestor mean they have common biochemical pathways.
Fitness
Fitness is the ability to survive and produce fertile offspring.
Natural selection 8 points
- Populations possess an enormous reproductive potential if all offspring produced also survived.
- Population size remains stable and it generally fluctuates around a constant size.
- Resources are limited and do not increase as the population grows larger.
- Individuals compete for survival because a growing population will exceed the available resources.
- There is variation among individuals in a population such as skin color.
- Much of the variation is heritable through passing down DNA.
- Only the most fit individuals survive,
otherwise known as survival of the fittest. - Evolution occurs as favorable traits accumulate in the population because the best adapted individuals leave more offspring.
Stabilizing selection
the bell curve favors an intermediate, like how the average height in humans is in the middle.
Directional selection
the favoring of traits that is at one extreme of the range. Traits at opposite extremes are selected against.
Industrial selection
the selection of dark- colored, melanic, varieties in various species of moths like the peppered moth as a result of industrial pollution. This is a specific type of directional selection.
Disruptive selection
this selection occurs when the environment favors extreme or unusual traits while selecting against common traits. For example, a certain environment may favor short and tall heights while the average height is selected against.
Sexual selection
the differential mating of males or females in a population.
Intersexual selection
females choose superior males, which increases the fitness of the offspring. Because females invest more energy into their offspring, they want to maximize the quality of their offspring by picking fit males.
Intrasexual selection
when males compete and fight with other males for better mating opportunities. Males increase fitness of offspring by maximizing quantity. Intrasexual selection favors traits like musculature, horns, large stature, etc.
Sexual dimorphism
the differences in appearance of males and females, which is a form of disruptive selection. This occurs because female choice leads to traits and behaviors in males that are favorable to females. Male traits like colorful plumage or elaborate mating behavior will be selected for by females.
Artificial selection
this is a form of directional selection carried out by humans when they breed favorable traits, and is not natural selection.
Sources of Variation
Mutation, Sexual reproduction, Diploidy, Outbreeding, Balanced polymorphism (Heterozygote advantage, Hybrid Vigor (heterosis), Frequency-dependant selection (minority advantage)), Neutral variation, Geographic variation
Mutation
new alleles could be introduced to the population with genetic mutations.
Sexual reproduction
genetic recombination such as crossing over, independent assortment, and random joining of gametes can occur during sexual reproduction.
Diploidy
Diploid organisms have two copies of each chromosome. In heterozygous conditions, the recessive allele is stored for later generations, and thus more variations are maintained in the gene pool.
Outbreeding
mating with unrelated partners results in mixing of different alleles and creating new allele combinations.
Balanced polymorphism
The maintenance of different phenotypes in a population. One phenotype is usually the best and thus has increased allele frequency. However, polymorphisms, the coexistence of two or more different phenotypes, can exist and be maintained:
Heterozygote advantage Hybrid Vigor (heterosis) Frequency-dependant selection (minority advantage)
Balanced polymorphism - Heterozygote advantage
When a heterozygote condition bears greater advantage than either homozygous conditions. For example, sickle cell anemia is a recessive trait, but being heterozygous for the trait confers resistance against malaria.
Balanced polymorphism - Hybrid Vigor (heterosis)
The superior quality of offspring resulting from crosses between two different inbred strains, species, or varieties of organisms. Hybrid superior quality results from reducing deleterious recessive homozygous conditions and increasing heterozygous advantage.
Balanced polymorphism - Frequency-dependant selection (minority advantage)
Occurs when least common phenotypes have a selective advantage. Common phenotypes are selected against. Rare phenotypes will increase in frequency and will then be selected against, repeating the cycle. For example, predators use search images of common phenotypes to find prey, allowing prey with rare phenotypes to escape. The rare prey phenotype eventually becomes common, and then the cycle repeats.
Neutral variation
these are variations that are passed down without any selective value, such as fingerprints in humans.
Geographic variation
variation of a species is dependent on climate or geographic conditions. A graded variation of a phenotype due to this is known as a cline. Variation from north to south environments is a north-south cline.
Gene flow
the introduction and removal of alleles from the population when individuals leave (emigration) or enter the population.
Genetic drift
the random increase and decrease of an allele by chance. Genetic drift has a larger effect on small populations.
Founder effect
when a small group of individuals migrate to a new location, the gene pool of the small group will be less than the original population. After successive generations, the genetic makeup will be unique from the original population.
Bottleneck effect
occurs when the population undergoes a dramatic decrease in size due to natural catastrophes or other events. The population is now vulnerable to genetic drift, and the gene pool is much smaller.
Nonrandom mating
individuals choose mates based upon their particular traits.
- Inbreeding - individuals mate with relatives. This changes genotype proportions but not allele frequency
- Sexual selection - females choose males based on superior traits
If allele frequencies remain constant from generation to generation
If allele frequencies remain constant from generation to generation, then there is no evolution. In this situation, the Hardy Weinberg equation can be used to determine allele frequencies for a population.
Hardy-Weinberg Equation Requirements
- No mutations - no new alleles can be
introduced to the population - No natural selection - the environment is not impacting allele frequencies, and so traits are neutral
- No gene flow - also happens as a result of no migration. An isolated population will have no gene flow
- Large populations - this decreases the effects of genetic drift
- Random mating - this decreases the chance of any allele from changing in frequency
Hardy-Weinberg Equation
p^2 + 2pq + q^2 = 1 (all individuals sum to 100%)
p + q = 1 (all alleles sum to 100%)
p = frequency of the dominant allele q = frequency of the recessive allele p2 = frequency of homozygous dominant q2 = frequency of homozygous recessive 2pq = frequency of heterozygous
Speciation
Speciation is the formation of new species. When gene flow ceases between two sections of a population, speciation begins. The first thing to happen in speciation is for gene flow between populations to be interrupted.
Species
a group of individuals capable of interbreeding.
Allopatric speciation
this speciation occurs when the population is divided by a geographic barrier. Interbreeding between two resulting populations is prevented as a result. The gene frequencies in the population can now diverge due to natural selection, mutation, and genetic drift. If the gene pool sufficiently diverges, the separated populations will not interbreed when the barrier is removed. If they cannot interbreed, that means a new species has formed. This form of speciation happens through:
- Dispersal - the group is isolated by being physically removed from the original location of the larger group
- Vicariance - the group is isolated by a geographic barrier but is in the same overall location of the larger group
Sympatric speciation
this is the formation of new species without the presence of geographic barriers. This can occur in a few different ways:
Balanced polymorphism, Polyploidy, Hybridization
Balanced polymorphism
natural selection due to polymorphism. Example: A population of insects has different colors. One color can camouflage to different substrates, but the insects in other colors cannot and will be eaten. Only insects with the advantageous color will mate as they are the ones that survive. The insects with this specific advantageous color are now isolated from other subpopulations
Polyploidy
possessing more than the normal two sets of chromosomes, such as 3n or 4n, is considered polyploidy. This can lead to reproductive isolation, such as in plants. For example, nondisjunction of a 2n plant species could occur during meiosis, resulting in gametes that are still diploid instead of haploid. These diploid gametes could self-pollinate or reproduce with other gametes that have the same diploid number to form a 4n zygote, but the diploid gametes cannot reproduce with the normal 1n gametes. This new 4n zygote would be reproductively isolated from the original 2n species, and thus speciation can occur. In plants, the polyploidy can be further categorized into: Autopolyploidy, Allopolyploidy
Autopolyploidy
when an organism has more than two sets of chromosomes, both of which are from the same parental species
Allopolyploidy
when a organism has more than two sets of chromosomes, but they come from different species
Hybridization
two different closely related species mate and produce a hybrid along a geographic boundary called a hybrid zone
Hybridization can result in more genetic variation. This means the hybrid can live beyond the range of either parents.
Adaptive radiation
the rapid evolution of many species from a single ancestor. This occurs when an ancestral species is introduced to an area where diverse geographic and ecological conditions are available for colonization.
Prezygotic isolation
this type of isolation prevents fertilization before mating is attempted, and so a zygote is not formed.
Habitat isolation, Temporal isolation, Behavioral isolation, Mechanical isolation, Gametic isolation
Habitat isolation
Species do not encounter each other because they live in different habitats, even if they live in the same geographical area
Temporal isolation
species reproduce at different seasons/times
Behavioral isolation
some species will not reproduce with each other if they do not perform the correct courtship rituals
Mechanical isolation
occurs when male and female genitalia are not compatible
Gametic isolation
male and female gametes do not recognize each other. The male gametes also may not survive in the environment of the female gametes
Postzygotic isolation
if a zygote does form, there are postzygotic methods to maintain reproductive isolation.
Hybrid inviability, hybrid sterility, hybrid breakdown
Hybrid inviability
the zygote fails to develop properly and dies before reaching reproductive maturity
Hybrid sterility
hybrids become functional adults but cannot reproduce
Hybrid breakdown
hybrids produce offspring that have reduced viability/ fertility. The hybrid’s children cannot reproduce
Divergent evolution
this type of evolution occurs when two or more species that originated from a common ancestor become increasingly different over time as a result of speciation.
Convergent evolution
this type of evolution occurs when two unrelated species evolve to share more similar traits due to adapting to a similar environment (analogous traits).
Parallel evolution
this type of evolution occurs when two related species make similar evolutionary changes after their divergence from a common ancestor.
Coevolution
this evolution occurs when two species each causes the other one to evolve, which results in the evolution of both species. An example of this is the coevolution of predators and prey, where the evolution of a more effective predator will cause the prey to evolve better ways to defend itself.
Macroevolution - Phyletic gradualism
this theory says that evolution occurs by the gradual accumulation of small changes. However, this is unlikely to be valid because intermediate stages of evolution are missing in the fossil record; fossils only reveal major changes in groups of organisms.
Macroevolution - Punctuated equilibrium
this theory says that evolutionary history consists of geologically long periods of stasis (stability) with little or no evolution followed by geologically short periods of rapid evolution. Absence of fossils revealing intermediate stages of evolution is considered data that confirms rapid evolutionary events.
General age of universe, solar system, fossils, organisms, etc.
The universe is 12-15 billion years old, the solar system is 4.6 billion years old, the earth is ~4.5 billion years old, the microfossils of prokaryotes are 3.6 billion years old, photosynthetic bacteria are 2.3 billion years old, and eukaryotes are ~1.8 billion years old.
Timeline, all steps
- Earth and the atmosphere formed through volcanoes
- Primordial seas formed
- Complex molecules were synthesized
- Polymers formed and self-replicated
- Organic molecules became protobionts
- Primitive heterotrophic prokaryotes formed
- Primitive autotrophic prokaryotes formed
- Ozone layer formed which ended abiotic chemical evolution
- Eukaryotes formed
Timeline - 1. Earth and the atmosphere formed through volcanoes
the atmosphere had CH4, NH3, CO, CO2, H2, N2, H2O, S, HCl, and HCN gases. There was little to no O2!
Timeline - 2. Primordial seas formed
As the earth cooled, gases condensed and formed a sea filled with water and minerals
Timeline - 3. Complex molecules were synthesized
the organic soup formed from inorganic compounds driven by energy from UV rays, lightning, heat, and radiation. The resulting organic compounds included acetic acid, formaldehyde, and amino acids
Timeline - 3. Complex molecules were synthesized - Oparin & Haldane
these scientists proposed the organic soup theory. They said that if there was O2 in the primordial atmosphere, no organic molecules would have formed because oxygen is very reactive. Oparin’s hypothesis was that the early Earth’s environment was reducing, which provides the chemical requirements to produce complex molecules from simple building blocks. An oxidizing environment would have broken the complex molecules apart
Timeline - 3. Complex molecules were synthesized - Stanley Miller
he tested Oparin’s theory and produced organic molecules. Miller & Urey sealed ammonia, methane, water, and hydrogen in a flask and simulated lightning; they created a simulated environment of the primordial Earth. The experiment produced several organic molecules, amino acids, and starting materials. However, no nucleic acids were made!
Timeline - 4. Polymers formed and self-replicated
simple monomers became polymers through dehydration condensation reactions. Proteinoids are abiotically produced polypeptides. If we heat amino acids in the lab, they will dehydrate and form proteinoids, confirming the validity of this step
Timeline - 5. Organic molecules became protobionts
protobionts were precursors of cells, they are metabolically active but unable to reproduce. Microspheres/liposomes and coacervates (spontaneously formed lipid or protein bilayer bubbles) are experimentally (abiotically) produced protobionts that have some selective permeable qualities. We can also produce microsomes in the lab: vesicle- like artifacts from reformed pieces of the endoplasmic reticulum if the cell is broken up
Timeline - 6. Primitive heterotrophic prokaryotes formed
they obtained energy by consuming other organic substances
Timeline - 7. Primitive autotrophic prokaryotes formed
heterotrophic prokaryotes mutated and gained the ability to produce their own food. An example of autotrophic prokaryotes is cyanobacteria
Timeline - 8. Ozone layer formed which ended abiotic chemical evolution
photosynthetic activity of autotrophs produced large amounts of oxygen. UV light and oxygen formed the ozone layer. The ozone layer absorbed UV light, thus blocking the energy needed for abiotic synthesis of organic materials. This causes the termination of primitive cells and abiotic evolution
Timeline - 9. Eukaryotes formed
the endosymbiotic theory explains that eukaryotic cells originated mutually among prokaryotes. The theory states that certain organelles like mitochondria and chloroplasts were once free-living prokaryotes. Other prokaryotes then phagocyted the mitochondria and chloroplast, and thus they lived in symbiosis.
Evidence for this theory is seen with thylakoid membranes of chloroplasts that resemble photosynthetic membranes of cyanobacteria.
Mitochondria and chloroplasts have double membranes and also have their own circular DNA that is not wrapped with histones, a trait of prokaryotes. The ribosomes of these organelles resemble those of bacteria, and they reproduce independently via a process similar to binary fission.
Composition of modern atmosphere and crust
The modern atmosphere is roughly 78% nitrogen (N2), 21% oxygen, 1% argon, and some less important gases. Earth’s crust is 47% oxygen and 28% silicon.
Vestigial structures
structures that appear to be useless but had ancestral function. For example, humans have vestigial appendixes and tails, horses have vestigial splints, and pythons have vestigial reduced leg bones
Mullerian mimicry
two or more harmful species that are not closely related but share one or more common predators, have come to mimic each other’s warning signals
Batesian mimicry
this is slightly different from Mullerian mimicry in that a harmless species has evolved to imitate the warning signals of a harmful species directed at a common predator
Gene pool
all the alleles for any given trait in the population
Parapatric speciation
this speciation occurs without a geographic barrier, so the population is continuous, but it still does not mate randomly. Individuals more likely to mate with geographic neighbors than with an individual farther out, so divergence may happen due to reduced gene flow and because of varying selection pressures across the population’s range. A population may occupy different niches that are adjacent and not isolated, so parapatric speciation could occur
Peripatric speciation
this is very similar to allopatric speciation in that a population is isolated and prevented from exchanging genes from the “main” one, but one of the populations is much smaller than the other, so it is subject to accelerated genetic drift along with differing selection pressures
Anagenesis/phyletic evolution
the gradual evolution of a species without any branching, is a straight path of evolution
Cladistics
a method of classification according to the proportion of measurable characteristics held in common between two organisms. The more characteristics they share, the more recently they diverged from common ancestor
Clade
a group of species that includes a common ancestor and all of its descendants. A clade is also known as a monophylum
Sere
a particular stage of an ecosystem
Mold
An organic matter that leaves an impression in rocks or in inorganic matter. Later, the organic matter decays and leaves a negative impression
Cast
a type of fossil formed when a mold is filled in
Deme
a small local population of the same species that regularly interbreed. For example, all the beavers along a specific portion of a river
Autotrophic anaerobes
chemosynthetic bacteria
Autotrophic aerobes
green plants and photoplankton
Heterotrophic aerobes
amoebas, earthworms, and humans
Heterotrophic anaerobes
yeast
Symbiosis
a relationship between two species. The relationship can be: mutualistic, commensalism, parasitism
Mutualistic Symbiosis
the relationship is beneficial to both species
Tick bird and rhinos are in a mutualistic relationship because the bird gets food (ticks) and the rhino loses its ticks.
Lichen (fungus and algae) is a mutualistic relationship because algae produces food for itself and the fungus via photosynthesis, while the fungus provides CO2 and nitrogenous wastes.
Nitrogen-fixing bacteria and legumes are another example because the legumes provide nutrients for bacteria while the bacteria fixes nitrogen for the legumes.
Protozoa and termites are an example too because protozoa digests cellulose for the termites, while termites protect and provide food for protozoa.
The last example is intestinal bacteria and humans. The bacteria utilize our food but provide us with vitamin K
Commensalism Symbiosis
the relationship is beneficial to one species and neutral to the other species
Examples are a remora and a shark, where the remora gets the food that the shark discards.
Another example are barnacles and whales, where the barnacle gets wider feeding opportunities by associating with a whale while the whale is unharmed
Parasitism Symbiosis
the relationship is beneficial to one species but detrimental to the other species
Parasites can be ectoparasites (cling to the exterior of the host) or endoparasites (live within the host).
All viruses are parasites and infect hosts.
Pathogenic bacteria are parasites that infect hosts as well, such as diphtheria infecting humans, anthrax in sheep, or tuberculosis in cows or humans.
There are also parasitic fungi that can infect hosts, such as ringworm which infects humans.
Tapeworms are well-known parasites that infect humans. Tapeworms are less dangerous, meaning the host will be more likely to live and allow the parasite to keep surviving. Thus, it is better for the parasite to not kill the host
Synapomorphies
shared traits derived from an evolutionary ancestor common to all members of a group
Analogous traits
similar characteristics resulting from convergent evolution, therefore they are not derived from a common ancestor
Law of parsimony
this is also known as Occam’s Razor, which states that the simplest explanation is most likely correct. Phylogenetic trees are constructed using the Law of Parsimony. The fewest number of changes with respect to synapomorphies is likely the most correct representation of reality
Monophyletic
the ancestral species and all its descendants
Paraphyletic
the ancestral species and some but not all descendants
Polyphyletic
the common ancestor of its members is not a part of the group
Simple reflexes
these are automatic and involve two nerves: afferent and efferent nerves. The response to stimulus is controlled at the spinal cord
Complex reflexes
these are automatic responses to significant stimulus. This is slower than simple reflexes because the nerves do not directly synapse with each other at the central nervous system like in simple reflexes. Instead, the nerves in complex reflexes are separated by an interneuron. Complex reflexes are controlled at the brain stem or even the cerebrum. An example of a complex reflex is the startle response which is controlled by the reticular activating system
Instinct
these are behaviors that are innate, or inherited. An example of an instinctual behavior is in mammals who care for their offspring by female parents.
Fixed action patterns (FAP)
these are innate behaviors that follow a regular, unvarying pattern. Fixed action patterns are initiated by a specific stimulus called a sign stimuli. The sign stimuli is called a releaser when it is between members of the same species. In many FAPs, the action will be completed even if the original sign stimuli is removed. The FAP is completed even if the original intent of the behavior cannot be fulfilled. Reflexes are technically FAPs. An example of a FAP is when a goose methodically rolls an egg lying on the edge back to the nest. Even if the egg is removed after the goose starts the FAP, it will still perform the action. The sign stimuli is the egg outside the nest. Another example of an FAP is male stickleback fish defending territory against any object with red undersides.
Imprinting
this is an innate program for acquiring specific behaviors only if the appropriate stimulus is experienced during the critical/sensitive period. Once acquired, the trait is irreversible. It can influence sexual selection. A well-known example of imprinting are when graylag goslings accept any moving object as their mother during the first day of life. Another example is salmon that return to their birthplace to breed based on imprinted odors associated with the birthplace.
Associative learning
this occurs when an animal recognizes (learns) that events are connected. This allows individuals to benefit from exposure to unexpected repeated events. There are several forms of associative learning.
Classical conditioning, trial-and-error learning (operant conditioning), Spatial learning
Classical conditioning
the most well- known example of classical conditioning are Pavlov’s dogs. Dogs naturally salivate when presented with food. This salivation caused by food is called the unconditioned response which is an innate reflex, and the food stimulus is the unconditioned stimulus. Pavlov then rings a bell when food is presented, and after some time, the dogs associated the bell sound with the food stimulus. However, ringing a bell with no food during the beginning of the experiment will not cause any response in the dog because the bell sound was still a neutral stimulus. At the end though, the dogs ended up salivating just at the sound of the bell without needing the food/unconditioned stimulus. Thus, the bell sound became the conditioned stimulus that will elicit a response even in the absence of the unconditioned stimulus. The salivation caused by the conditioned stimulus is called the conditioned response/reflex.
Trial-and-error learning (operant conditioning)
this is another form of associative learning that occurs when an animal connects its own behavior with either a punishment or reward. If the animal’s response is rewarded/ reinforced, the animal will repeat its behavior. If the animal’s response is punished, the animal will avoid that behavior. Punishment and reward can either be positive or negative (positive punishment, negative punishment, positive reward, negative reward). Positive means adding something, and negative means removing something.
Trial-and-error learning (operant conditioning) - Positive punishment
adding something bad to decrease a behavior (e.g. hitting an animal when it bites someone)
