Question 1

Which hypothesis best explains the origin of the nuclear envelope and endoplasmic reticulum in eukaryotes?

Accepted Answer

They were derived from the infoldings of the plasma membrane.

Question 2

Which of the following is NOT evidence supporting the endosymbiotic theory for the origin of mitochondria?

Accepted Answer

Mitochondria are larger than most eukaryotic cells.

Question 3

According to the endosymbiotic theory, which sequence of events led to the origin of eukaryotes?

Accepted Answer

Evolution of nucleus, endosymbiosis of mitochondria, endosymbiosis of chloroplast.

Question 4

Which group is paraphyletic and does NOT include all descendants of a single common ancestor?

Accepted Answer

Protists

Question 5

What is the main ecological role of photosynthetic protists in aquatic ecosystems?

Accepted Answer

They are primary producers, contributing to nearly half of Earth's net primary production (NPP).

Question 6

Why are mitochondria genes more closely related to eubacterial genes than to eukaryotic nuclear genes?

Accepted Answer

Because mitochondria originated from an engulfed eubacterium via endosymbiosis.

Question 7

Which of the following best describes the evolutionary advantage of the haploid-diploid life cycle in eukaryotes?

Accepted Answer

It allows for increased genetic variation through recombination, independent assortment, and segregation.

Question 8

Multicellularity arose independently in several eukaryotic lineages. Which of the following is NOT a crown group where multicellularity evolved?

Accepted Answer

Brown algae

Question 9

Under which environmental conditions is sexual reproduction favored over asexual reproduction according to the changing environment hypothesis?

Accepted Answer

Dynamic, unpredictable environments

Question 10

Which of the following statements about protists is TRUE?

Accepted Answer

Protists are paraphyletic and represent some, but not all, descendants of a single common ancestor.

Question 11

Which of the following is a direct result of the transition from prokaryote to eukaryote?

Accepted Answer

Improved control of gene expression due to the nuclear membrane and endoplasmic reticulum

Question 12

Which evidence supports the endosymbiotic origin of chloroplasts?

Accepted Answer

Chloroplasts have DNA sequences closely related to cyanobacteria.

Question 13

Which process increases genetic variation in eukaryotes?

Accepted Answer

Meiosis

Question 14

What is the primary benefit of multicellularity in protists?

Accepted Answer

It allows for specialization and division of labor among cells.

Question 15

Which of the following organisms could be eukaryotes with a nucleus, internal membrane system, and mitochondria ONLY (no chloroplasts)?

Accepted Answer

Animal

Question 16

Why do many protists undergo meiosis when food is scarce or population density is high?

Accepted Answer

To increase genetic variation, which may help offspring cope with rapidly changing environments.

Question 17

Which formula represents the alternation of haploid and diploid phases in the eukaryotic life cycle?

Accepted Answer

$$2n \xrightarrow{meiosis} n \xrightarrow{fertilization} 2n$$

Question 18

Which of the following statements about the origin of chloroplasts is correct?

Accepted Answer

Chloroplasts originated from the engulfment of a photosynthetic cyanobacterium.

Question 19

Which lineage is NOT considered a crown group derived from protists?

Accepted Answer

Brown algae

Question 20

What is the relationship between photosynthetic protists and carbon cycling in aquatic ecosystems?

Accepted Answer

They are responsible for almost half of the total net primary production (NPP) on Earth.

Origin of Eukaryotes and Protist Diversity

Study Guide - Practice Questions