Cycle 8

Question 1

Q: What is macro-evolution?

Answer 1

A: Macro-evolution refers to evolutionary changes occurring over extended time scales, like discovering new species or dividing existing species into groups.

Question 2

Q: What is the Last Universal Common Ancestor (LUCA)?

Answer 2

A: LUCA is the hypothesized ancestral cell from which the three domains of life (Bacteria, Archaea, and Eukarya) originated.

Question 3

Q: What is a phylogenetic tree?

Answer 3

A: It is a representation of evolutionary relationships, where each node is a common ancestor, and branching shows divergence.

Question 4

Q: How do you identify the Most Recent Common Ancestor (MRCA) in a phylogenetic tree?

Answer 4

A: Locate the closest shared node for the groups of interest by tracing paths backward toward the root.

Question 5

Q: What is the Morphological Species Concept?

Answer 5

A: It defines species based on physical similarities, such as body size or fur color, but struggles with cryptic species, sexual dimorphism, and convergent evolution.

Question 6

Q: What is the Biological Species Concept?

Answer 6

A: A species is an interbreeding group of individuals, reproductively isolated from others, producing viable, fertile offspring. This concept struggles with asexual organisms and ring species.

Question 7

Q: What is the Ecological Species Concept?

Answer 7

A: Species are groups adapted to specific environmental resources or niches, but this fails for organisms with stage-specific ecological roles, like frogs.

Question 8

Q: What is the Phylogenetic Species Concept?

Answer 8

A: It defines species as populations with a recent evolutionary history, requiring detailed knowledge of ancestry.

Question 9

Q: What is allopatric speciation?

Answer 9

A: A single population is split into two by a geographic barrier. Over time, they evolve separately and can no longer mate.

Question 10

Q: What is reinforcement in speciation?

Answer 10

A: It is the selection favoring prezygotic isolation to prevent mating between populations when postzygotic isolation has already occurred.

Question 11

Q: Does secondary contact always lead to speciation?

Answer 11

A: No, secondary contact can either undo speciation (fusion) or accelerate it (reinforcement).

Question 12

Q: Why is the idea “humans are descended from chimpanzees” incorrect?

Answer 12

A: Humans and chimpanzees share a MRCA but evolved through separate lineages.

Question 13

Q: What is clinal variation?

Answer 13

A: Clinal variation occurs when environmental or geographical factors create a gradient of traits across populations, influenced by restricted gene flow and differing selective pressures.

Question 14

A: Clinal variation occurs when environmental or geographical factors create a gradient of traits across populations, influenced by restricted gene flow and differing selective pressures.

Answer 14

A: Geographic variation can restrict gene flow and favor the evolution of specific traits suited to local environments, resulting in gradual changes across regions.

Question 15

Q: What is the result of clinal variation?

Answer 15

A: A gradient of characteristics evolves along a geographic gradient, with populations gradually differing based on their location.

Question 16

Q: What is a cline?

Answer 16

A smooth pattern of variation across a geographical gradient

Question 17

Q: What are reproductive barriers?

Answer 17

A: Reproductive barriers prevent gene flow between populations, maintaining their distinctiveness. These can be physical (geographic isolation) or behavioral (mating preferences).

Question 18

Q: What are examples of physical reproductive barriers?

Answer 18

A: Physical barriers include mountains, rivers, or other geographical separations that isolate populations.

Question 19

Q: What are examples of behavioral reproductive barriers?

Answer 19

A: Behavioral barriers include differences in mating calls, rituals, or preferences that prevent interbreeding between populations.

Question 20

Q: How do clinal variation and reproductive barriers relate?

Answer 20

A: Clinal variation often results from restricted gene flow due to reproductive barriers, which prevent populations in different regions from exchanging genes freely.

Question 21

Q: Why are reproductive barriers important in evolution?

Answer 21

A: They allow populations to diverge and adapt to their specific environments, potentially leading to speciation.

Question 22

Q: What is a ring species?

Answer 22

A: A ring species forms when a population spreads in a ring around an area it cannot live in. Changes happen as they spread, so populations at the ends of the ring can’t mate with each other.

Question 23

Q: Why are ring species still considered the same species?

Answer 23

A: Even though some groups can’t mate directly, the populations in between can mate and pass genes, so they all share the same gene pool.

Question 24

Q: What are pre-zygotic isolating mechanisms?

Answer 24

A: They prevent the formation of a zygote altogether, stopping species from mating successfully.

Question 25

Q: What are the types of pre-zygotic isolation?

Answer 25

1. Ecological Isolation: Species live in the same area but in different habitats.
2. Behavioral Isolation: Mating signals or behaviors are not recognized.
3. Temporal Isolation: Species mate at different times (day, season, etc.).
4. Mechanical Isolation: Differences in reproductive structures prevent mating.
5. Gametic Isolation: Sperm and egg are incompatible, so fertilization doesn’t occur.

Question 26

Q: What are post-zygotic isolating mechanisms?

Answer 26

A: A zygote is formed, but it either doesn’t survive or can’t reproduce.

Question 27

Q: What are the types of post-zygotic isolation?

Answer 27

1. Hybrid Inviability: The zygote dies because the genes are too different to develop properly.
2. Hybrid Sterility: The hybrid grows but can’t produce offspring (e.g., mule).
3. Hybrid Breakdown: Hybrids can reproduce, but their offspring have problems (e.g., infertility).

Question 28

Q: What is sympatric speciation?

Answer 28

A: New species evolve in the same area without geographic barriers. For example, polyploidy (extra chromosome sets) can create new species in plants.

Question 29

Q: What is secondary contact?

Answer 29

A: Secondary contact happens when two previously isolated populations meet again.

Question 30

Q: What happens when reproductive isolation does not occur?

Answer 30

Fusion: Populations resume interbreeding.
Result: Gene flow continues, populations remain as one species, and speciation slows down.

Question 31

Q: What happens when reproductive isolation occurs?

Answer 31

Reinforcement of Speciation: Populations are less likely to interbreed, favoring individuals who mate within their population.
Result: Speciation speeds up due to reduced hybrid formation.