Ap Biology: evolution
Carolus Linnaeus
(1707-1778) Founder of taxonomy, the branch of biology concerned with naming and classifying organisms. Developed two part system of naming organisms. --> contrasts with scala naturae as he grouped similar species into increasingly general categories --> NOT DESCRIBING EVOLUTION but a pattern of their creation
What are 4 types of Evidence for evolution?
1.Direct Observations 2.Fossil Record 3.Homology 4.Biogeography
From these four observations, what two inferences did Darwin make?
1.Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than do other individuals. 2.This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations.
THREE KEY POINTS OF NATURAL SELECTION
1.Natural selection is a process in which individuals that have certain heritable traits survive and reproduce at a higher rate than do other individuals because of those traits. 2.Over time, natural selection can increase the frequency of adaptations that are favorable in a given environment--> can only diminish or amplify heritable traits that differ in a population 3.If an environment changes, or if individuals move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species.
What can we learn from the direct observation of the soapberry bug and S. aureus?
1.natural selection is a process of editing not creative mechanism (drugs can't create resistance rather than selecting for resistant individuals) .2in species that produce new generations in short periods of time, evolution by natural selection can occur rapidly 3.natural selection depends on time and place. It favors those characteristics in a genetically variable population that provide an advantage in the current, local environment.
Define evolution broadly and then give a narrower definition, as discussed in the overview.
A broad definition of evolution would be descent with modification with a more narrow description of the process by which species accumulate differences from their ancestors as they adapt to different environments over time; also defined as a change in the genetic composition of a population from generation to generation.
vestigial structures
A feature of an organism that is a historical remnant of a structure that served a function in the organism's ancestors for example snakes arose with a pelvis and leg bones of their ancestors, but have no purpose today.
systematics
A scientific discipline focused on classifying organisms and determining their evolutionary relationships.
What is summarized in an evolutionary tree?
An evolutionary tree indicates the evolutionary relationships among groups of organisms, indicating common ancestry and adaptations that occurred. branching process exhibited on a tree could explain the large morphological gaps that sometimes exist between related groups
Do antibiotics cause bacteria to become resistant? Explain your response.
Antibiotics have become less effective because a drug does not create resistant pathogens; it selects for resistant individuals that are already present in the population. For example, some strains of MRSA are resistant to multiple antibiotics (probably because bacteria can exchange genes with members of their own and other species
It is important to remember that differences in heritable traits can lead to differential reproductive success. This means that the individuals who have the necessary traits to promote survival in the current environment will leave the most offspring. How can this differential reproductive success affect the match between organisms and their environment?
Different reproductive success can affect a match between an organism and its environment because it determines how well the organism can handle environmental changes. For example, an organism that has traits that give its offspring an advantage in escaping predators or tolerating harsh physical conditions, the frequency of those genes within the next generations will increase and therefore the majority of offspring will occupy an environment where those traits are an advantage
Old Testament - Creationism
Earth ~6000 years old; perfect species individually designed by God Aristole: viewed species as fixed or unchanging and concluded that life forms could be arranged on a ladder or scale of increasing complexity, later called the scala of naturae
Charles Darwin
English naturalist 1831: joined the HMS Beagle for a 5-year research voyage around the world Collected and studied plant and animal specimens, bones, fossils Notable stop: Galapagos Islands Darwin waited 30 years before he published his ideas on evolution Charles Darwin (1859): On the Origin of Species by Means of Natural Selection
Theory of Natural Selection:
Evolution is change in species over time. 1.There is overproduction of offspring, which leads to competition for resources. •Leads to differential survival 2.Heritable variations exist within a population. 3.These variations can result in differential reproductive success. More favorable phenotypes survive. 4.Over generations, this can result in changes in the genetic composition of the population. Remember: Individuals do NOT evolve! Populations evolve Natural selection accounts for the differences that are held within related organisms as one species might share common DNA and ancestry, but some might have a mutation that increased survival rate and branch off, still maintaining shared DNA, but with a different, effective trait.
Descent with Modification
Evolutionary change is based on the interactions between populations & their environment which results in adaptations (inherited characteristics) to increase fitness
1. Direct Observations
Examples: Insect populations become resistant to pesticides (DDT) Antibiotic-resistant bacteria (MRSA) Peppered moth (pollution in city vs. country) MRSA strain or the beak in Soapberry bugs that most effectively picks up seeds (either three flat lobes, and its seeds are much closer to the fruit surface than are the seeds of the plump, round fruit of the native balloon vine) which resulted in shorter beaks that feed on goldenrain tree than those who feed on balloon vine.
2. Fossil Record
Fossils = remains or traces of organisms from past Found in sedimentary rock Show evolutionary changes that occur over time and origin of major new groups of organisms Fossil record gives evidence for evolution as the record documents the pattern of evolution showing past organisms differed from present day organisms that many species have become extinct. Fossils also exhibit evolutionary changes that have occurred in various groups of organisms. the pelvic fossil in stickleback fish have become reduced in size as shown in the study of fossils of the fish over time or the fossil record of cetaceans (whales, dolphins, porpoises) are closely related to even toed ungulates (hippos, pigs, deer, cows)
Explain the role of fossils in rock strata as a window to life in earlier times.
Fossils are found in sedimentary rocks formed from sand and mud settled to the bottom of lakes and swamps. Fossils in a stratum provide evidence of some of the organisms that populated Earth at the time the layer formed.
How would Georges Cuvier have explained the appearance of the record of life shown in the rock strata?
George Cuvier developed the scientific study of fossils or paleontology. (older the stratum the more disimilar the fossils) He would have explained the appearance of the record shown in rock strata by speculating that each boundary between strata represented a sudden catastrophic event, such as a flood, that destroyed many of the species living in that area and reasoned that those areas were lated repopulated by different species immigrating from other areas (from his initial findings of from one layer to the next some species appeared while other disappeared. He launched his opinions because he did not support the idea of evolution.
inheritance of acquired characteristics
His next mechanism or theory titles inheritance of acquired characteristics stated that an organism could pass these modifications to its offspring. Lamarck reasoned that the long muscular neck of a giraffe had evolved over many generations as giraffes stretch their necks higher.
There is competition for resources; not all offspring survive
If all of these offspring and their descendants survived to maturity, they would carpet the surrounding land surface, making it impossible for other species to coexist
James Hutton
James Hutton proposed that Earth's geological features could be explained by gradual mechanisms such as valleys being formed by rivers wearing through rocks.
Charles Lyell:
Incorporated Huttons thinking into his proposal that he same geological processes are operating today as in the past and at the same rate.--> earth is old
Evolutionary Fitness
Individuals with more favorable phenotypes more likely to survive and produce more offspring, and pass traits to future generations measured by reproductive success If environment changes or individuals move to new environment, new adaptations and new species may arise.
What is biogeography? How is it affected by continental drift and the presence of endemic species?
It was affected by the continental drift because when pangea or the supercontinent that formed near the end of the Paleozoic era when plate movements brought all the landmasses of Earth together split, it separated species and organisms. For example, when horses were studied their fossils were found in north america dating back 5 million years ago, when the continents were not connected, henceforth the biogeographical aided scientists to find the original environment of horses. Biogeography is also affected by endemic species or species that are confined to a specific geographic area as colonies close to the mainland gave rise to new species as they adapted to their new environments (which also explains why two islands with similar environments in distant parts of the world tend to be populated with species related to those of the nearest mainland.
Use and Disuse
Lamarck compared living species with fossil forms as he had found several lines of descent each a chronological series of older to younger fossils leading to a living species. Use and disuse was the idea that parts of the body that are used extensively become larger and stronger while those that are not deteriorate. --> giraffe stretching its neck--> why its gotten larger
MRSA
MRSA is methicillin-resistant Staphylococcus aureus, a flesh-eating strain of bacteria that are formidable pathogens.
Thomas Malthus
Malthus: More babies born than deaths Consequences of overproducing within environment = war, famine, disease (limits of human pop.) Struggle for existence
Jean-Baptiste Lamarck (1744-1829)
Published theory of evolution (1809) Use and disuse theory inheritance of acquired characteristics believed that evolution happened because organisms have an innate drive to become more complex
Even though incorrect, why were Lamark's findings important?
Recognized that species evolve, although explanation was flawed Lamarack thought that evolution happens because organisms have an innate drive to become more complex but Darwin rejected that idea but agreed that variation was introduced into the evolutionary process in part of inheritance of acquired characteristics. (Today, however, our understanding of genetics refutes this mechanism: Experiments show that traits acquired by use during an individual's life are not inherited in the way proposed by Lamarck). He is most recognized for the fact that organisms are well suited for life in their environments and can be explained by gradual evolutionary change, and he did propose a testable explanation for how this change occurs.
How did it become so dangerous? Explain the evolution of MRSA's resistance to methicillin.
Since penicillin several other antibiotics have saved millions of lives but by 1945 over 20% of the S.aureus strains were resistant to penicillin as they contain penicillinase that destroys penicillin. In 1959 doctors than used methicillin as it was a promising new antibiotic at the time however, within two years methicillin resistant strains of S.aureus were observed. Methicillin works by deactivating an enzyme that bacteria uses to synthesize their cell walls and some S.aureus populations include cells able to synthesize their cell walls using different enzyme that was not affected by methicillin, causing resistance to become more common as these individuals survived the methicillin treatment and reproduced at higher rates.
strata
Strata or rock layers formed when new layers of sediment cover older ones and compress them.
Homologous structures
Structures in different species that are similar because of common ancestry. Forelimbs in mammals are considered homologous because they share the same basic structure from a common ancestor
These variations (traits) are heritable.
The asian elephant and the african elephant are closely related species but branched off from the common ancestry as they had new adaptations and produced offspring passing them down
Darwin's Finch Collection
The birds were all about the same size, but the shape and size of the beaks of each species were different. thought they resembled those of the mainland of South America
Biogeography
The scientific study of the past and present geographic distributions of species.geographic distribution of a species Species in nearby geographic areas resemble each other Continental drift and Pangaea explains similarities on different continents
How is natural selection influenced?
When such advantages increase the number of offspring that survive and reproduce, the traits that are favored will likely appear at a greater frequency in the next generation. natural selection resulting from factors such as predators, lack of food, or adverse physical conditions can lead to an increase in the proportion of favorable traits in a population.
How does convergent evolution give rise to analogous structures?
With convergent evolution analogous structures can arise through environmental influences. The sugar glider's in Australia look very similar to flying squirrels in North America. Sugar gliders have several other characteristics that make their marsupial more closely related to other Australian marsupials. Although they evolved independently of each other from different ancestry these two mammals have adapted to similar environments in similar manners, to create analogous structures through convergent evolution.
3. Species overproduce.
all species can produce more offspring than their environment can support and many of these offspring will fail to survive A single puffball fungus can produce billions of spores that give rise to offspring.
Adaptations
are inherited characteristics of an organism that enhances its survival and reproduction in a specific environment.
fossils
are preserved remnant or impressions of an organism that lived in the past that play an important role in rock strata
ecosystem stability determines the rate of direction of evolution
biotic and abiotic environments can remain more or less stable -environments can experience major disruptions and change quickly or change slowly over time -populations are less likely to evolve in environments that remain stable over long periods of time
an example of fossil record
cetaceans mammalian order that includes whales dolphins and porpoises some DNa evidence proves that ceateans are closely related to even toed ungulates a group that includes hippopotamuses, pigs and cows
3. Homology
characteristics in related species can have underlying similarity even though functions may differ Homologous structures show evidence of evolution because they exhibit shared features that lead us to believe common ancestry is present among the organisms. one structure's anatomical resemblances could not have been present if a new species arose, or it would be unlikely. similar structures develop to have different structures. In comparing early stages of development in different species reveals additional anatomical homologies not visible in adult organisms. Throat arches eventually developed into parts of ears and throat in humans and gills in fish, but their similarities in structure exhibit common ancestory
What did Darwin state was evolution?
descent with modification mechanism for evolution is natural selection he attributed the unity of life in the descent of all organisms from an ancestor that lived in the past and then new organisms branched off by living in different environments which caused diverse modifications
Prokaryotes (oldest fossils) -->
eukaryotes (fish - amphibians - reptiles - birds - mammals) Transitional forms = links to modern species
Gradualism
geologic change results from slow & gradual, continuous process-Hutton
Analogous structures:
having characteristics that are similar because of convergent evolution, not homology for example ability to glide through air evolved independently in the flying squirrel and the sugar glider.
Variations in traits exist.--> example
individuals in this population of Asian ladybird beetles vary in color and spot pattern. Natural selection may act on these variations only if (1) they are heritable and (2) they affect the beetles' ability to survive and reproduce
heritability
is the ability to pass on adaptations to successive generations organisms with favorable traits=higher in population
Uniformitarianism
is the belief that processes occurring today at the same rate thought of by Charles Lyell. The importance of this concept is that it implied the world is much older than believed at the time if geologic change resulted from slow, continuous actions rather than from sudden events.
Convergent evolution
is the process by which similar environmental conditions select for similar traits in different populations of different species over time
Darwin and the HMS Beagle
observed that plants and animals in temperate regions of south america more closely resembled species living in the South American tropics than species living in temperate regions of Europe which correlated with the fossils found observed how the earthquake on the coast of Chile --> environmental pressure--> resulted in rocks along the coast had been thrust upward by several meters inferred that rocks containing the fossils must have been raised there by many similar earthquakes -->reinforced that physical evidence did not support the traditional view that Earth was only a few thousand years old
Overproduction
of offspring leads to competition for resources
competition
organisms struggle with other organisms to get limited resources - organisms will compete for resources such as space, food, mates, nutrients, and light -differences in phenotype will determine how competitive an organism is which leads to differential survival
Alfred Russell Wallace
published paper on natural selection first (1858)
selective pressure
refers to any biotic or abiotic factors influencing survivability. (disease, predation, climate, and food availability) changing environments introduce different selective pressures on populations -individual fitness is relative to the environmental condition phenotypes selected for can be selected against when environmental conditions change (vice versa)
variation
refers to genetic differences among organisms within a population -mutations and sexual reproduction increase variation within population
fitness:
refers to the ability of an organism to survive and produce fertile offspring any phenotype that decreases chances of survival negatively impacts fitness any phenotype that increases chances of survival and reproduction positively impacts fitness
reproductive success
refers to the production of offspring reproductive success over several generations is a component of evolutionary fitness
example of convergent evolution
selective pressure of similar aquatic environments can select for streamlined bodies in verbrates like fish and mammals
Molecular Homologies
similar DNA and amino acid sequences
Embryonic homologies
similar early development (eg. vertebrate embryos with tail & pharyngeal pouches)
Endemic Species
species that are confined to a specific geographic area as colonies close to the mainland gave rise to new species as they adapted to their new environments (which also explains why two islands with similar environments in distant parts of the world tend to be populated with species related to those of the nearest mainland)
Phylogney
the evolution history of a species of or related group
artificial selection
the selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits commonly used in agricultural and economic practices. for example growing certain crops with specific characteristics or breeding certain animals for sport or sale may result in phenotypes that would not naturally exist --> can lead to more or less diversity
