WEEK 3 (cladistics, phylogeny, early life on earth)

What are some hypothesis coming out of the Cambrian explosion?

- new predator/prey relationships -rise in atmospheric oxygen -evolution of Hox gene complex

What are the closest relatives of birds over evolutionary history? Explain your answer.

Dinosaurs are the closest relatives over all of history because of the evidence in their bone structures.

What characters would we find in mitochondria and chloroplasts of eukaryotes, if these organelles were the result of endosymbiosis of prokaryotes? a. plasma membrane, nucleus and ribosomes b. nucleus, DNA and ribosomes c. plasma membrane, nucleus and cilia d. nucleus, ribosomes and cilia e. plasma membrane, DNA and ribosomes.

E. plasma membrane, DNA and ribosomes.

Has has early taxonomy utilized racism?

Early taxonomists would overgeneralize races into 5 "varieties". White Europeans were put on the top. There is absolutely no biological basis. We also cannot ignore the impact that racism in pseudoscience still has consequences today (eugenics).

What role did endosymbiosis play in the evolution of plants and animals? What evidence do we see for this?

Endosymbiosis played a role in developing eukaryotic cells capable of photosynthesis and respiration. We see this from the mitochondria and chloroplasts who have membranes, ribosomes and DNA.

molecular clock

Model that uses DNA comparisons to estimate the length of time that two species have been evolving independently using the idea that genes evolve in a constant rate

do coyotes evolve from gray wolves or vice versa?

We can only interpret them as having an extinct common ancestor that was neither coyote nor gray wolf.

The most direct ancestors of land plants were probably a. kelp (brown alga) that formed large beds near the shoreline b. green algae c. photosynthesizing prokaryotes (cyanobacteria) d. liverworts and mosses

b. green algae

Linnaean Taxonomy

classify groups using ranks that are hierarchal where each group is in another. Domain, Kingdom, Phylum, Class, Order, Genus, Species.

What is the evidence that RNA, rather than DNA, was the first genetic material? a. RNA contains U in place of T b. RNA could have evolved into DNA c. RNA can replicate more accurately d. RNA has both information storage and catalytic properties e. all the proto-cells on early earth had RNA

d. RNA has both information storage and catalytic properties

Explain the role of each of the following events leading up to life on earth: ● Synthesis of Organic Compounds ● Abiotic Synthesis of Macromolecules ● Protocells ● Self-replicating RNA

Synthesis of organic compounds: Organic compounds could form from simpler molecules in a reducing environment like early earth's atmosphere. Abiotic synthesis of macromolecules: Abiotic synthesis of RNA monomers was possible with just simple precursors. Polymers could have formed spontaneously when in contact with hot rocks, sand, or clay. Protocells: spontaneously forming vesicles could have been formed, especially in contact with montmorillonite. These had the capabilities of replication, metabolism and could keep a chemically stable environment. Self-replicating RNA: RNA is capable of being a catalyst (ribozymes) including catalyzing their own self-replication.

character state

The observed condition of a character, such as presence or absence of lungs or arrangement of petals.

MRCA

most recent common ancestor

does the sequence of branching indicate the age of the organism?

no, unless specified the diagram should only be interpreted in terms of descent patterns

Synapomorphy

shared derived character

Systematics

study of the diversification of taxa; classification of organisms using evidence of evolutionary history

Cambrian explosion

sudden appearance of fossils resembling modern phyla in the fossil record during the Cambrian period.

phylogenetic tree

A family tree that shows the evolutionary relationships thought to exist among groups of organisms. it is a HYPOTHESIS

Cladistics

A phylogenetic classification system that uses shared derived characters and ancestry as the sole criterion for grouping taxa.

maximum parsimony

A principle that states that when considering multiple explanations for an observation, one should first investigate the simplest explanation that is consistent with the facts. Occam's razor. the simplest explanation is most likely.

polyphyletic group

A taxonomic grouping consisting of several species that lack a common ancestor (more work is needed to uncover species that tie them together into a monophyletic clade). (ex: rhinos and elephants)

Though many organisms are diploid (having 2 copies of each chromosome, one inherited from each parent), whole genome duplication events are fairly common in plant taxa, resulting in species with 4, 6, 8 or even 12 copies. What impact might a whole genome duplication event have on an organism's reproduction and its evolutionary trajectory?

Advantageous traits that are in the genome could be duplicated, which would give offspring a higher chance of survival and lead to a new evolutionary lineage. Also, having duplicated genomes could make the organism reproductively isolated from the parent generation, making them a new species.

Scala Naturae

An Aristotelian concept of a "ladder" of life in increasing complexity with humans at the top.

Why is Australia so weird: Explain in 3-4 sentences how the process of continental drift impacted the evolution of unique lineages on the Australian continent.

Australian fauna are so different from the rest of the world because of continental drift. Marsupials originated most likely in Asia and went to Australia while Antarctica and South America were still joined. When Australia broke off, it took the marsupials with it, which diversified into the species we had today. Placental mammals (eutherians) were left on all the other continents and Australia had less.

Which of the following statements cannot be interpreted from the tree? a. the group containing elephants and anteaters evolved first in history b. the group with pangolins and lynxes are the last mammals to evolve in history c. bats, camels, rhinos, pangolins and lynxes share a common ancestor d. a and b e. b and c

D. a and b. phylogenetic trees show ancestry and relations, not time.

binomial nomenclature

Classification system in which each species is assigned a two-part scientific name. Genus + species

Phylogeny

Evolutionary history of a species

Miller-Urey Experiment

Experiment that found that organic molecules can form in a strongly reducing atmosphere.

sister taxa

Groups of organisms that share an immediate common ancestor and hence are each other's closest relatives.

Synapomorphies of mammals

Hair, mammary glands, and differentiated teeth (specialized to their diet)

orthologous genes

Homologous genes passed in a straight line from one generation to the next.

paralogous genes

Homologous genes that are found in the same genome as a result of gene duplication.

To what extent should we take cultural and political milieu of historical people into account when assessing them? How do we weigh the positives and negatives of historical people when assessing them?

IMO, historical people do need to be help accountable for their actions and racist views, but that does not mean that we should disregard their contributions towards science. We can appreciate the science without memorializing them as a person.

Is the gray wolf and coyote MRCA a fossil?

Not neccessarily

In the classic pea experiment performed by Austrian monk Gregor Mendel, the "Father of Genetics" in the 18th century, tall plants are dominant over short plants and green pea pods are dominant over yellow pods. A short plant that is heterozygous for green pea pods is crossed with a plant that is heterozygous for both traits. What is the genotype for each of the parent plants? What is the probability that an offspring is short with green pods?

Parental genotypes: TtGg and ttGg Offspring probability for short with green pods: 3/8

monophyletic

Pertaining to a group of taxa that consists of a common ancestor and all of its descendants. A monophyletic taxon is equivalent to a clade.

horizontal gene transfer

The transfer of genes from one genome to another through mechanisms such as transposable elements, plasmid exchange, viral activity, and perhaps fusions of different organisms.

taxon (taxa, plural)

a category into which related organisms are placed

paraphyletic group

a group that includes an ancestral population and some of its descendants, but not all. (ex: "fish")

outgroup

a lineage that is known to diverge before the lineage that includes the species we are studying

Cladogram

a phylogenetic tree showing clades based on synapomorphies

Mass extinctions: a) The Cretaceous-Tertiary boundary (or KT boundary) marks a huge shift in life on earth caused by one of the 5 mass extinctions. Which clades of organisms were impacted most by this extinction event, and what are the main drivers that may have caused it? b) Some scientists argue that we are currently in the middle of a 6th mass extinction event. What evidence would we need to confirm or refute this hypothesis?

a) the clades impacted by this event were marine species and all the dinosaurs. One of the causes could be an asteroid, as indicated by layer of iridium. The cloud of debris that would have covered the earth and atmosphere could also be a cause b.) To confirm or refute this we would need to be able to accurately measure the amount of species being lost. We would also need to assess the effect of climate change and habitat destruction and learn about new species that are yet undiscovered.

Based on the following cladogram of marine mammalian pokemon, answer the following questions: a) Are Ursidae more closely related to the Dugongidae or Phocidae? How do you know? b) The Pinnipedia family is a grouping called a "polytomy" in which more than two clades meet at a branch point/common ancestor. Why might a polytomy exist in a tree? c) The blue circled taxa have evolved tusks. Based on the cladogram, would you say it's more likely for this trait to be ancestral or derived (how many character changes would be needed)? Based on this, would "tusk having organisms" in this cladogram be considered monophyletic, polyphyletic or paraphyletic group?

a. Urisidae are more closely related to the Phocidae because they have a MRCA b. A polytomy exists where there is an unresolved pattern of evolution (aka, there's not enough info) c. It is more likely a derived trait because the ancestors do not have that trait. This is polyphyletic because it is a derived trait in multiple branches.

polytomy

an unresolved pattern of divergence

Pleisomorphies

ancestral characters

photosynthesizing eukaryotic cells have chloroplasts and mitochondria. which time events most likely describe the evolution of these organisms? a. ancestral anaerobic prokaryote engulfs a photosynthetic prokaryote b. ancestral anaerobic prokaryote engulfs an anaerobic heterotrophic prokaryote and then engulfs a photosynthetic prokaryote c. ancestral anaerobic prokaryote engulfs a photosynthetic prokaryote and then engulfs an anaerobic heterotrophic prokaryote d. ancestral anaerobic prokaryote engulfs an aerobic heterotrophic prokaryote and then engulfs a photosynthetic prokaryote

d. ancestral anaerobic prokaryote engulfs an aerobic heterotrophic prokaryote and then engulfs a photosynthetic prokaryote

What organism is the most advanced? a. apis mellifera (european honey bee) b. Amybystoma tigrinum (tiger salamander) c. E. coli d. Homo sapiens e. none of the above

e. each species has had the same amount of evolutionary time to evolve, so making comparisons like these don't mean anything.

character state

one of the variant conditions of a character