Chapter 25 terms and concepts

Question 1

Describe steps by which simple cells may have originated from non-living materials

Answer 1

1. The abiotic (nonliving) synthesis of small organic molecules, such as amino acids and nitrogenous bases
2. The joining of those organic molecules into macromolecules, such as proteins and nucleic acids
3. The packaging of these molecules into protocells
4. The origin of self-replicating molecules that eventually made inheritance possible

Question 2

Protocell

Answer 2

An abiotic precursor of a living cell that had a membrane-like structure and maintained an internal chemistry different from its surroundings.

(Abiotically produced vesicles have even demonstrated simple reproduction and metabolism, homeostasis)

Question 3

Ribozymes (and which genetic material came first, DNA or RNA)

Answer 3

The first genetic material was most likely RNA, not DNA. RNA is much more efficient with replication, and makes fewer errors in replication, and thus is hypothesized to precede DNA given it’s ability to create descendant molecules.

RNA plays a central role in protein synthesis, but also functions as an enzyme-like catalyst. Ribozymes are enzyme-like catalysts (ie - an intron that catalyzes its removal during RNA splicing)

Question 4

Why do some scientists believe that RNA, rather than DNA, was the first genetic material?

A. RNA has both information storage and catalytic properties.
B. RNA contains uracil in place of thymine.
C. RNA could have evolved into DNA.
D. RNA can replicate more accurately than DNA.
E. All the proto-cells on early Earth contained RNA.

Answer 4

A

Question 5

Explain what fossils are, how they are dated, and what the fossil record can reveal about life’s history

Answer 5

Fossils are remnants of organisms that have been preserved in (most likely) sedimentary rock

Question 6

Macroevolution

Answer 6

Applies to major evolutionary changes, such as whole taxonomic groups over long periods. The development of large-scale structures and traits that go significantly beyond the different traits in microevolution

Question 7

Microevolution

Answer 7

Minor evolutionary changes within a species that allow for increased fitness in a certain specific environment. These changes are due to allele frequencies that occur over time

Question 8

Types of fossils (from most to least abundant)

Answer 8

(Most abundant)
1. Trace fossils: indirect evidence left by an organism: footprints, feces, habitats
2. Molds/casts: an impression of an organism, a cast is a mold filled with sedimentary rock.
3. Replacement: The original organic material of the organism is replaced by mineral crystals that leave replicas of the organism
4. Petrified: Empty pore spaces are filled in by minerals, such as petrified wood
5. Amber: Tree sap which is preserved traps the entire organism. Sap hardens into amber
6. Original material: mummification or freezing preserves the original organism

Question 9

Why is the fossil record biased?

Answer 9

It only has preserved species that live for a long time, were abundant and widespread in certain environments, had hard structures that could be preserved, etc.

Question 10

How are fossils dated?

Answer 10

Radiometric dating, which focuses on the decay of radioactive isotopes that decay at fixed rates.

C-14 half-life is 5730 years, and when the ratio is compared to the fixed C-12 isotope, you can date the fossil.

ratio is 1/16 of a fossil, then the fossil would be 5730 * 4 (for 4 half lives) = 22,920 years old

Question 11

What can the fossil record tell us about life’s history?

Answer 11

It shows that there have been great changes in the kinds of organisms on Earth at different points in time. It also shows the age of the Earth and the organisms that have inhabited it

Question 12

The clock analogy

Answer 12

1. The origin of the solar system and Earth, followed by the Hadean period (4.6 bya)
2. The Archaean period (4 bya - 2.5 bya), where prokaryotes emerged (3.5 bya). At end of archean period, atmospheric oxygen formed (~2.75 bya) due to photosynthetic bacteria
3. The Proterozoic period (2.5 bya - 0.6 bya), where single-celled (~1.8 bya) then multicellular eukaryotes (~1 bya) form. After multicellular eukayrotes, animals emerge toward the end of the Proterozoic era (750 mya)
4. The last period, the Phanerozoic period (~600 mya- present) is constructed into three subgroups: the Paleozoic, Mesozoic, and Cenozoic eras, where the colonization of land and humans emerged.

Question 13

Stromatolites

Answer 13

Oldest known fossils; which are mats of cyanobacteria, new generations form on top of older. ~3.5 billion years old

Prokaryotes were sole inhabitants for more than 1.5 billion years

Question 14

Endosymbiont theory

Answer 14

Where the first Eukaryotes are hypothesized to come from, where a prokaryote engulfs a small cell that evolved into a mitochondrion

Question 15

Endosymbiont

Answer 15

The small cell that was engulfed and lived within the cell that engulfed it, which was the host cell

Question 16

Serial Endosymbiosis

Answer 16

The hypothesis that the origin of eukaryotes consisting of a sequence of endosymbiotic events in which mitochondria, chloroplasts, and other structures were derived from smaller engulfed prokaryotic bacteria.

It is postulated that mitochondria were developed before plastids

Question 17

Photosynthetic eukaryotes contain both mitochondria and
chloroplasts. Which sequence of events most likely describes
the evolution of this group?

A. Ancestral anaerobic prokaryote engulfs an aerobic heterotrophic
prokaryote and then engulfs a photosynthetic prokaryote.

B. Ancestral anaerobic prokaryote engulfs a photosynthetic prokaryote and then engulfs an aerobic heterotrophic prokaryote.

C. Ancestral anaerobic prokaryote engulfs an anaerobic heterotrophic prokaryote and then engulfs a photosynthetic prokaryote.

D. Ancestral anaerobic prokaryote engulfs a photosynthetic prokaryote and then engulfs an anaerobic heterotrophic prokaryote.

Answer 17

A

Question 18

Origin of multicellularity

Answer 18

A second wave of diversification occurred when multicellularity occurred and gave rise to algae, plants, fungi, and animals

the oldest multicellular eukaryotes are small red algae about ~1.2 bya

Question 19

What is the key evidence that supports an endosymbiotic origin of mitochondria and plastids?

Answer 19

Inner membranes of both organelles are similar to living bacteria

DNA structure / cell division of organelles are similar to bacteria

Both plastids and mitochondria transcribe and translate their own DNA

Ribosomes are more similar to bacteria than eukaryotic ribosomes

Question 20

What are the consequences of continental drift on species?

Answer 20

It alters the habitats in which organisms live, as the physical and environmental climate is affected drastically. This can drive some species into extinction while providing other species to flourish

They are affected by climate change that results from continent shifts. Continents shift from one portion of the globe to another, causing species that inhabit them to die off, adapt, or migrate

Separation of land masses causes allopatric speciation

Question 21

Consequences of mass extinctions

Answer 21

These events cause unfavorable environments for organisms and these organisms die off (habitat being destroyed, or environment being changed in some other way that is unfavorable and unsustainable for a species, or a new species emerges that outcompetes)

Question 22

When did the 5 previous mass extinction events occur?

Answer 22

“rapid cooling” : 443 mya (Paleozoic)

Multiple causes: 359 mya (Paleozoic)

Volcanism: 252 mya (Mesozoic) - Permian, which killed 96% of marine life

Multiple causes : 201 mya (Mesozoic)

Meteor: 66 mya (Cenozoic)

Question 23

Why did mammals diversify after dinosaurs went extinct?

Answer 23

There was less competition for food/prey, and were less subject to predation by dinosaurs as well (as they were more complex and capable organisms before extinction).

Question 24

Adaptive radiations

Answer 24

A period of evolutionary change in which groups of organisms form many new species whose adaptations will allow them to fill different ecological roles in their communities

Question 25

Why do adaptive radiations occur after mass extinctions?

Answer 25

Survivors adapt to the new ecological landscape where many niches have been left vacant by extinct species. Survivors then adapt to fit those niches, as they faced little competition from other species

Question 26

It is difficult to estimate the current extinction rates of today. Why?

Answer 26

Because the fossil record is a biased source, it may not give the full picture of the previous mass extinction events (although that is all the info we have to go on)

Question 27

What are the causes of current species decline?

Answer 27

Abnormal global warming and climate change

Question 28

What is the relationship between global temperature and extinction rates?

Answer 28

Extinction rates seem to gradually increase with warming temperatures.

Question 29

Evo-devo

Answer 29

Research at the interface between evolutionary biology and developmental biology

Question 30

Heterochrony

Answer 30

Evolutionary change in the timing or rate of an organism’s development (ie. changes in growth rates of different body parts during an organism’s development can have profound effects on the organism’s form

Question 31

Paedomorphosis

Answer 31

An adult organism retaining juvenile features of its evolutionary ancestors

Question 32

Homeotic genes (one class of homeotic genes: Hox genes)

Answer 32

Master regulatory genes determine basic features as were limbs will developed, etc

Hox genes specifically regulate positional information in an animal embryo which allows cells to develop in a particular location

Question 33

What facilitated the origin of novel morphological forms?

Answer 33

New developmental genes that arose from gene duplication events

Question 34

Drosophila, or the fruit fly (what happened, and which change: changes in sequence/regulation of genes can result to major morphological change?):

Answer 34

Hox gene “Ubx” in Drosophila insects suppressed 100% of limb development, while Ubx gene found in shrimp only suppressed 15%. Researchers found specific mutations in the Artemia (shrimp) gene that contribute to limb suppression, which is seen more thoroughly in Drosophila genes. (changes in nucleotide sequence)

Question 35

Did changes in the sequence or regulation of genes cause more morphological changes in organisms?

Answer 35

Regulation, as changes to regulation is hindered to one cell type (while changing the nucleotide sequence of a gene may affect its function wherever the gene is expressed), and thus will have fewer harmful side effects

Question 36

Three spined stickle back fish and changes to gene regulation

Answer 36

Marine stickleback fish have a pair of spines on their backs, while lake sticklebacks do not (lake sticklebacks are not subject to predation)

This is the result of Pitx1 homeotic gene that is not expressed in lake fish, but expressed in marine fish. The genetic sequences have not changed.

Question 37

Show how novel and complex structures can arise from descent with modification

Answer 37

Since evolution is a process where new forms arise only by slight modification of existing forms, novel biological structures (like a patch of pigmented cells that detect light) can evolve in many stages to more complex structures

a patch of pigmented photosensitive cells evolved into complex eyes after evolving independently many times, and these structures (both novel and complex) are still observed today in molluscs with different complexities of eyes.