Evolution and Ecosystems Flashcards
- Describe and Explain the endosymbiotic theory
It is thought that life arose on earth around four billion years ago. The endosymbiotic theory states that some of the organelles in today’s eukaryotic cells were once prokaryotic microbes. In this theory, the first eukaryotic cell was probably an amoeba-like cell that got nutrients by phagocytosis and contained a nucleus that formed when a piece of the cytoplasmic membrane pinched off around the chromosomes. Some of these amoeba-like organisms ingested prokaryotic cells that then survived within the organism and developed a symbiotic relationship. Mitochondria formed when bacteria capable of aerobic respiration were ingested; chloroplasts formed when photosynthetic bacteria were ingested. They eventually lost their cell wall and much of their DNA because they were not of benefit within the host cell. Mitochondria and chloroplasts cannot grow outside their host cell.
Summarize the evidence in support of the theory for the evolution of eukaryotic cells.
- Chloroplasts are the same size as prokaryotic cells, divide by binary fission, and, like bacteria, have Fts proteins at their division plane. The mitochondria are the same size as prokaryotic cells, divide by binary fission, and the mitochondria of some protists have Fts homologs at their division plane.
- Mitochondria and chloroplasts have their own DNA that is circular, not linear.
- Mitochondria and chloroplasts have their own ribosomes that have 30S and 50S subunits, not 40S and 60S.
- Several more primitive eukaryotic microbes, such as Giardia and Trichomonas have a nuclear membrane but no mitochondria
- explain how fossils are dated. Explain the significance of leading fossils.
One of the most common technique is radiometric dating which is based on the decay of radioactive isotopes. Each radioactive isotope has a fixed rate of decay. An isotope’s half-life, the number of years it takes for 50 percent of the original sample to decay, is unaffected by temperature, pressure, and other environmental variables. Fossils contain isotopes of elements that accumulated in the organisms when they were alive, E.g., the carbon in a living organism includes the most common carbon isotope, carbon-12, as well as a radioactive isotope, carbon-14. When the organism dies, its stops accumulating carbon, ad the carbon-14 that it contained at the time of death slowly decays and becomes another element, nitrogen 14.Thus, by measuring the ratio of carbon-14 to total carbon or to nitrogen-14 in a fossil, we can determine the fossils age.
- explain why living fossils did not undergo much change and give examples.
At the time of death, the organism got , causing their bodies (or in some cases their bones) to be extremely well preserved so that they could maintain their structure for hundreds of years, where they were found by humans. Methods of preservation include: o Silicification/ petrification (Silifizierung bzw. Verkieselung/ Versteinerung): silica (Kieselsäure) from weathered volcanic ash is gradually incorporated into partly decayed wood o Phosphitylation (Phosphatierung): bones and teeth are preserved on phosphate deposits o Pyritization (Verkiesung): pyrite (Pyrit) replaces hard remains of the dead organism o Tar pit (Teergrube): animals fall into and are trapped in mixture of tar and sand o Trapped in amber (Bernstein): gum (Harz) from conifers traps insects and then hardens o Limestone (Kalkstein): calcium carbonate from the remains of marine plankton is deposited as a sediment that traps the remains of other sea creatures
- explain the significance of transitional fossils and give examples (i.e., Archaeopteryx)
Transitional fossils (“missing/ connecting links“) (= Übergangs-/ Mosaik-/ Brückenform) are intermediate forms that show traits of two different taxonomic groups. They suggest that one (original) group may have given rise to the other (newly developing) group by evolutionary processes. One of the main examples is the Archaeopteryx, the most primitive bird known. It serves as a transitional fossil between the dinosaur and the modern bird, with it sharing jaws with sharp teeth, a forelimb with three fingers with grasping claws, a long bony tail and various other skeletal features putting it in closer relation to the dinosaur than a bird, with the Archaeopteryx only possessing a bird’s small size, broad wings, and an ability to fly or glide.
- describe and explain molecular biological (e.g., DNA hybridization) methods that can be used to determine phylogenetic relationships.
A phylogenic relationship means that the two species in question that do share a phylogenic relationship have had a common ancestor in their past.
DNA hybridization
1. first the DNA of each source is extracted, and the two strands are separated (denatured) by heat treatment => hydrogen bonds are broken 2.the single strands of the two sources are then put together, whereupon they join up (hydrogen bonds are formed between complementary bases), sometimes with the complementary strand from their own source, but sometimes with the complementary strand from the other source (forming hybrid DNA) 3.the double-stranded hybrid DNA containing strands from the two sources will separate at a lower temperature, because the hydrogen bonding which holds the two strands together is weaker, as some of the bases fail to pair
4.the two sources are thought to be more closely related, the closer the temperature at which the hybrid DNA separates is to the temperature used to separate the DNA of the two sources (great similarity of base sequence => more hydrogen bonds form) => crude measure of DNA relatedness!
- describe and explain immunological (e.g., precipitation test) methods that can be used to determine phylogenetic relationships.
A phylogenic relationship means that the two species in question that do share a phylogenic relationship have had a common ancestor in their past.
1.A laboratory animal (e.g., a rabbit) is injected with human serum.
2.The rabbit then produces antibodies in response to the human serum proteins.
3. These antibodies react with the serum proteins of various vertebrates with precipitations of different intensities.
The extent of precipitation with the human serum in response to which the antibodies have been formed is taken to be 100%. The varying degree of precipitation illustrates the match between the surface proteins of the serum and the antibodies. The degree of precipitation is a measure of the extent to which the tested serum proteins are congruent with the human serum proteins; correspondingly, this is interpreted as an indication of the similarity of the responsible genes and therefore a measure of the relationship between the organisms tested, i.e., their common origin. On a biochemical level, these proteins are homologous (having the same relation, position, or structure)-
- describe and explain how the recorded genetic changes in living organisms over many generations can be used as evidence of evolution.
o Anatomy. Species may share similar physical features because the feature was present in a common ancestor (homologous structures).
o Molecular biology. DNA and the genetic code reflect the shared ancestry of life. DNA comparisons can show how related species are.
o Biogeography. The global distribution of organisms and the unique features of island species reflect evolution and geological change.
o Fossils. Fossils document the existence of now-extinct past species that are related to present-day species.
o Direct observation. We can directly observe small-scale evolution in organisms with short lifecycles (e.g., pesticide-resistant insects).
To adapt to a certain environment, a species will genetically alter itself (and its appearance) to better be adapted to its environment. An example is the peppered moth population found in England at the time of the industrial revolution. Due to the fact that the surplus of factories was spewing out excessive amounts of pollution, the surrounding forests got covered in a layer of soot. This left the natural-coloured moths in a precarious position, as their light brown colour left them highly visible in the surrounding darkened forest, making them easy prey. Through genetic variation they adapted, splitting into a darkened moth and a light moth. This change was genetic. Because the light moths were even more of a target, they soon went extinct. But because the dark moths were more suited to the sooted environment, they were able to survive due to their more advantageous genetic traits. Evolution occurred.
- discuss the significance of vestigial organs as indicators of evolutionary trends
These ‘useless’ body-parts, otherwise known as vestigial organs, are remnants of lost functions that our ancestors possessed. They once represented a function that evolved out of a necessity for survival, but over time that function became non-existent. Since those useless body parts aren’t needed anymore, a lack of vestigial organs would imply that the organism developed further, evolution occurring because the new environment does no longer require the vestigial organs.
- describe and explain the biogeographical evidence of evolution.
The distribution of organisms around the world lends powerful support to the idea that modern forms evolved from ancestral populations. Biogeography is the study of the geographical distribution of species, both present-day and extinct. It stresses the role of dispersal of species, a point of origin across pre-existing barriers. Studies from the island populations indicate that flora and fauna of different islands are more closely related to adjacent continental species than to each other.
- use given data to draw a cladogram or interpret it.
A cladogram gives a hypothetical picture of the actual evolutionary history of the organisms. A cladogram indicates the relationships between organisms descended from a common ancestor. The temporal aspect of a phylogenetic tree, however, is missing from a cladogram.
- Find the outgroup (the “odd one out”)
- Proceed along the line, always trying to find one species that differs from the rest
- Create branches that illustrate the differentiation of one species from the rest
- use given data to draw a phylogenetic tree or interpret it.
A Phylogenic tree gives an actual representation of the evolutionary history of the organisms.
- Find the outgroup (the “odd one out”)
- Proceed along the line, always trying to find one species that differs from the rest
- Find the temporal order of the species
- Create branches that illustrate the differentiation of one species from the rest
10 describe the hierarchical classification and name the taxonomic categories. Moreover, explain the binominal nomenclature giving an example
In 1748, Swedish botanist and anatomist Carolus Linnaeus published “Systema naturae“, his taxonomic classification of all plants and animals known at the time. Linnaeus introduced scientific names for each species that consisted of two parts:
Example: Panthera (capitalized) pardus (both parts are italicized)
genus + specific epithet unique for each species
(= Gattung) + (= Artepitheton)
-> This two-part format of the scientific name is called binominal nomenclature.
In the Linnaean system, species and genera are grouped further into a hierarchical system of higher taxonomic categories.
Hierarchical classification
Hierarchical classification:
- Species (e.g., Homo Sapiens)
- Genus (e.g., Homo)
- Family (e.g., Hominidae)
- Order (e.g., Primates)
- Class (e.g., Mammals)
- Phylum (e.g., Vertebrates )
- Kingdom (e.g., Animals)
- Domain (e.g., Eukarya)
- describe and explain how different species have evolved from a single ancestral species/ a specific trait could have developed according to Lamarck’s theory of evolution
Lamarck: Lamarck believed that organisms are not passively altered by their environment. Instead, a change in the environment causes changes in the needs of organisms living in that environment, which in turn causes changes in their behaviour. Altered behaviour leads to greater or lesser use of a given structure or organ: continued use would cause the structure to increase in size and become more highly developed over several generations, whereas disuse would cause it to shrink or even disappear. Lamarck claimed that such acquired characteristics were heritable. (Today, our understanding of genetics tells us that traits acquired by use during an individual´s life is not inherited!) The result is the continuous, gradual change of all organisms, as they became adapted to their environments; the physiological needs of organisms, created by their interactions with the environment, drive Lamarckian evolution. Lamarck also thought that evolution happens because organisms have an innate drive to become more complex (inneres Bedürfnis, Vervollkommnungstrieb).
