T8 - Tree of life

Question 1

What are the 7 properties of life that all living organisms share?

Answer 1

1. cellular organization (made up of 1 or more cells)
2. energy and metabolism (able to extract energy from their environment - photosynthesis, foods)
3. Reproduction (able to reproduce to form new generations)
4. Heredity and evolution (have genes/alleles, can change because of mutations)
5. Growth and development (we grow and go through different stages - insects go through metamorphosis)
6. Regulation and homeostasis (maintaining the right equilibrium state - blood pH, temperature, blood nutrients)
7. Response to stimuli (signaling molecules or responding to heat and changes in temperature)

Question 2

Why are viruses not considered organisms?

Answer 2

• No cellular organization
• No internal metabolism
• No growth or development

They depend on the host to reproduce

Question 3

What is a fossil?

Answer 3

Preserved remnant or impression of an organism that lived in the past

Organisms that lived a long time ago

Question 4

What is a stromatolite?

Answer 4

Layered rock that results from the activities of photosynthetic prokaryotes that bind thin films of sediment together (bacteria)

Question 5

What element is on Earth life based on?

Answer 5

Carbon

• highly abundant on earth and in atmosphere

Question 6

What are the 4 necessary steps from organic molecules to protocells?

Answer 6

1) Abiotic synthesis of small organic molecules - monomers; amino acids, nitrogenous bases

2) Polymerization of small molecules into macromolecules - polyers; proteins, nucleic acids

3) Packaging of these molecules into protocells (vesicles) - precursors of cells with only some components

4) The origin of inheritance through the transmission of self-replicating molecules

• DNA can be replicated when cells divide (forming of gametes)
• transmission of some info needs cells that can ‘copy’ themselves

Question 7

What are protocells?

Answer 7

Does not contain genetic info (DNA)

Droplet with membranes (bilayer of fatty acids) that maintained an internal chemistry different from that of the environment

Not living organisms - not cells but have many properties of life

Question 8

What is primordial/prebiotic soup?

Answer 8

Hypothetical set of conditions that led to the transition from the abiotic world to the biotic world

As long as you have the three basic building blocks; water, monomers, energy (to create bonds between all the smaller ones)
Especially in the presence of water

Question 9

What was Stanley Millers experiement?

Answer 9

The artificial synthesis of organic matter under conditions that mimicked the early Earths atmosphere (methane, ammonia, hydrogen) and lighting (energy)

• Found that under these conditions, there was a synthesis of formaldehyde, hydrogen cyanide, amino acids and hydrocarbons from abiotic molecules
• ∴ the building blocks came from the reactions of all the gases

Question 10

How do protocells exhibit some properties of life?

Answer 10

• Vesicles can divide spontaneously (reprod)
• Replication reactions inside vesicle (Internal metabolism)
• Vesicles can increase in size (growth)
• Membranes can eb selectively permeable (regulation)
• Membranes can perform metabolic reactions using external molecules (response to env.)

Question 11

Why do we sometimes say it is an RNA world?

Answer 11

First organisms were thought to have RNA, not DNA

RNA probably came before both DNA and proteins

Question 12

Why does the question exist asking which came first, enzymes or nucleic acids? What is the answer?

Answer 12

Because proteins (enzymes) are synthesized from DNA and RNA

but DNA and RNA are synthesized through enzymatic reactions

RNA molecules are able to function as enzymes and catalysts (ribozymes)

• ribozymes can then copy other RNA molecules and self replicate
  ∴ RNA most likely came first

Question 13

What is inheritance?

Answer 13

The passing of RNA of a splitting vesicle to daughter vesicles

• Some error in RNA replication and some variation (mutations) in replication rate allows for evolution through NS

Question 14

What can the relative and absolute age of fossils inform us on?

Answer 14

The evolutionary history of organisms

• many fossils belong to species that no longer exist and went extinct
• some fossils ressemble organisms that still exist today
• organisms can undergo very rapid morphological changes

Question 15

What is biostratigraphy vs radiometric dating?

Answer 15

Biostratigraphy = determination of relative age via sedimentary rocks

• imprecise/inaccurate
• placing a fossil on top of one another where the most recent (youngest) is at the top and the oldest is at the bottom

Radiometric dating = determination of absolute age via magmatic rocks

• precise and accurate

Question 16

What is faunal succession?

Answer 16

Specific vertical sequence of fossilized flora and fauna that can be identified reliably over wide horizontal distances

Question 17

How do we define biozones?

Answer 17

With the help fo specific fossil composition

• intervals of time of geological strata

Question 18

What kinds of species are good biomarkers?

Answer 18

Species that have very specific ecological requirements, that lived for a very short geological period

Biomarkers = diagnostic species (helps put a date on sediments)

Question 19

How does radiometric dating occur?

Answer 19

Uses changes in the isotope composition of organisms during their transition state to fossils, and magmatic rocks

Question 20

What is an isotope? What is a stable isotope vs an unstable one?

Answer 20

Isotope = elements with the same number of protons but different number of neutrons

Unstable isotope (parent) 14C decays into daughter isotope 14N at a constant known rate

Stable isotope 12C in the fossil remains constant until the fossil is discovered

Question 21

WHat is the isotopic half life?

Answer 21

Amount of time it takes for 50% of the parent isotope (14C) to decay into its daughter isotope (14N)

Question 22

Why is the fossil record incomplete?

Answer 22

Many fossils were destroyed over time without yet being discovered

There is a bias towards species that existed for long evolutionary times and those with hard shells/skeletons

• was found that for some periods of time, there are no fossils perhaps due to erosion (erosion = no sediments)

Question 23

What can discontinuity in the fossil record indicate?

Answer 23

Can reflect important geologicalm ecological and evolutionary events

• plate tectonics, erosion, decrease in rate of sedimentation
• changes in climate/habitat, retreat of seas and glaciers (changes in sea levels may lead to migration of species)
• species colonization, phenotypic evolution, extinction

Question 24

What were the different lifestyles like on the Burgess Shale?

Answer 24

Burgess shale was a paelontological site containing sediments with large diversity of fossilized animals

Benthic = living on the sediments

Endobenthic = living in the sediments

Nektonic = swimming freely

Question 25

What was the Cambrian explosion? What arose from it?

Answer 25

Many animal phyla today appeared around the same time (535-525 mya) increasing the morphological diversity

• Soft bodied to hard shells organisms demonstrated new defensive adaptations, transition from grazers/suspension feeders to predators and new body plans and prey/predator relationships

Question 26

What are adaptive radiations?

Answer 26

Period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in their communities (roles/niches)

Question 27

What formed due to the evolutionary success of bilateral symmetry?

Answer 27

• Anterior sensing organs (development of a nervous system/reproductive system)
• Anterior predation appendages (prey capturing/feeding)
• Posterior appendages for movement (swimming, crawling, flying) -> feathers

Question 28

What can cause mass extinctions?

Answer 28

Changes in temperature, massive volcanic eruptions, meteorites

• all lead to a cascade of dramatic ecological events
• always followed by new adaptive radiations and many new families and genera

Question 29

What happens once the number of species or members or a taxonomic level reach an asymptote (apparent maximum)?

Answer 29

Chances that you will find a new species are high, but low that we will discover a new class (something of a higher/superior class to a species)

Question 30

What suggests that all living organisms might share a common ancestor?

Answer 30

All living organisms synthesize and use only L optical isomers of amino acids (out of the 2 configs of molecules L or D)

• LUCA (Last Universal Common Ancestor) contained a genetic code which we can hypothesize based off this that all living organisms share a common genetic code
• LUCA was not necessarily the first living organism - the latest organism that is ancestral to all existing organisms we know today

Question 31

Where did LUCA likely live? What might this mean?

Answer 31

Likely living near deep-sea vents that are deprived of oxygen but rich in CO2 and H2

This means that LUCA was living in anaerobic conditions - using cellular respiration but in the absence of oxygen

Question 32

What is phagocytosis?

Answer 32

The ability to trap something from outside and eat

It develops the membrane so it can do folding in the cell (developing a nuclear envelope)

Question 33

How did eukaryotes evolve? What structures differ between them?

Answer 33

Evolved from prokaryotes within the Archaea branch

Differs in a presence of;

• cytoskeleton = help give structure
• endomembrane system = transportation of vesicles (golgi appartus, ER)
• Nucleus

Question 34

What is serial endosymbiosis?

Answer 34

Prokaryotic cells engulfed by an ancestral archaea cell

• bacteria trapped inside, once its inside it becomes a eukaryote which gave rise to the mitochondria

Question 35

What is a mitochondrion or plastid?

Answer 35

Organelles possesing a circular DNA, their own transcription/translation proteins, ribosomes/membrane proteins similar to bacteria

• Can do aerobic respiration for the cell further adding metabolic systems inside which increases the chance of capturing/using oxygen for glucose

Question 36

What are the benefits of a mitochondrion?

Answer 36

Cell gains a new metabolic system (aerobic respiration)W

Question 37

What is the colonial hypothesis?

Answer 37

Colonies form through the cooperation of unicellular organisms of the same species

• Cells fail to separate (or separate and then rejoin)
• specialization can occur (where some have different functions - 2 cells that can communicate and work together for transport for example)

Question 38

What is the symbiosis hypothesis?

Answer 38

Cells from different species establish a mutually benefical and long term association (not likely)

• requires both genomes to merge into a unique one