Biology Test Practice Test: Video 1 Answers (25 Questions) — Questions and Answers

Question 1: Which cytoskeletal element is primarily responsible for maintaining cell shape in animal cells?

Microtubules
Intermediate filaments
Microfilaments (actin) (Correct answer)
Centrioles

Correct answer: Microfilaments (actin)

Actin microfilaments form a network beneath the plasma membrane that supports cell shape and enables cell movement.

Question 2: During meiosis, homologous chromosomes exchange genetic material through which process?

Crossing over (recombination) (Correct answer)
Disjunction
Replication
Synapsis

Correct answer: Crossing over (recombination)

Crossing over occurs during prophase I when non-sister chromatids of homologous chromosomes exchange segments at points called chiasmata.

Question 3: What is a nucleosome?

A small membrane-bound organelle containing enzymes
A single-stranded RNA molecule in the nucleus
DNA wrapped around a histone octamer (Correct answer)
The site of ribosome assembly

Correct answer: DNA wrapped around a histone octamer

A nucleosome consists of approximately 147 base pairs of DNA wrapped around a core of eight histone proteins, forming the basic unit of chromatin.

Question 4: What is the primary role of cyclin-CDK complexes in the cell cycle?

Repairing DNA double-strand breaks
Regulating progression through cell cycle checkpoints (Correct answer)
Separating sister chromatids at the centromere
Synthesizing histones for DNA packaging

Correct answer: Regulating progression through cell cycle checkpoints

Cyclin-dependent kinase (CDK) complexes phosphorylate target proteins to drive the cell through key transitions such as G1/S and G2/M checkpoints.

Question 5: Which process allows cells to engulf large particles or other cells by forming membrane vesicles?

Pinocytosis
Phagocytosis (Correct answer)
Exocytosis
Transcytosis

Correct answer: Phagocytosis

Phagocytosis is a form of endocytosis in which the cell membrane engulfs large particles like bacteria, forming a phagosome.

Question 6: Which term describes the process by which a species' population becomes so small that it loses genetic diversity and faces increased extinction risk?

Inbreeding depression
Genetic drift
Genetic bottleneck (Correct answer)
Founder effect

Correct answer: Genetic bottleneck

A genetic bottleneck occurs when a population is drastically reduced, causing loss of allelic diversity and increasing vulnerability to extinction.

Question 7: Which IUCN criterion classifies a species as Critically Endangered based on population size?

Fewer than 10,000 mature individuals
Fewer than 50,000 mature individuals
Fewer than 250 mature individuals (Correct answer)
Fewer than 1,000 mature individuals

Correct answer: Fewer than 250 mature individuals

Under IUCN criteria, a population of fewer than 250 mature individuals qualifies a species for Critically Endangered status.

Question 8: Which human activity is considered the single largest driver of tropical deforestation globally?

Logging for timber
Agricultural conversion for livestock and crops (Correct answer)
Mining operations
Urban expansion

Correct answer: Agricultural conversion for livestock and crops

Agricultural conversion—especially for cattle ranching, palm oil, and soy—accounts for the majority of tropical forest loss worldwide.

Question 9: Which treaty provides the primary international framework for regulating trade in endangered wild plants and animals?

Ramsar Convention
CITES (Correct answer)
Kyoto Protocol
Convention on Biological Diversity (CBD)

Correct answer: CITES

CITES (Convention on International Trade in Endangered Species) regulates and in some cases bans international trade in threatened species.

Question 10: Which principle explains why a larger reserve will typically support more species than a smaller one?

Island biogeography theory (Correct answer)
Competitive exclusion principle
Intermediate disturbance hypothesis
Bergmann's rule

Correct answer: Island biogeography theory

Island biogeography theory predicts that species richness increases with area because larger areas support larger populations and more diverse habitats.

Question 11: What term describes plants that complete their life cycle in two growing seasons?

Perennial
Annual
Ephemeral
Biennial (Correct answer)

Correct answer: Biennial

Biennials such as carrots and foxglove grow vegetatively in their first year and flower, set seed, and die in their second year.

Question 12: Which plant hormone is primarily responsible for fruit ripening?

Gibberellin
Auxin
Cytokinin
Ethylene (Correct answer)

Correct answer: Ethylene

Ethylene is a gaseous hormone that triggers fruit ripening, leaf abscission, and other senescence processes.

Question 13: Which of the following best describes apical dominance in plants?

Flowers always develop at the tips of branches
The largest leaves are always found at the top of the plant
The apical bud suppresses the growth of lateral buds (Correct answer)
The root tip grows faster than the shoot tip

Correct answer: The apical bud suppresses the growth of lateral buds

Apical dominance occurs when the apical meristem produces auxin that inhibits the growth of lateral (axillary) buds below it.

Question 14: Which plant tissue type provides structural support and is composed of dead cells at maturity?

Meristematic tissue
Sclerenchyma (Correct answer)
Parenchyma
Collenchyma

Correct answer: Sclerenchyma

Sclerenchyma cells have thick, lignified secondary cell walls and are dead at functional maturity, providing rigid mechanical support.

Question 15: What is the role of the Casparian strip in plant roots?

Forces water through the symplast into the vascular tissue (Correct answer)
Prevents backflow of water into the soil
Stores starch
Absorbs mineral ions by active transport

Correct answer: Forces water through the symplast into the vascular tissue

The Casparian strip is a waxy band in endodermal cell walls that blocks the apoplastic pathway, forcing water and solutes through the symplast into the stele.

Question 16: A scientist observes that a population of beetles has become resistant to an insecticide over 20 generations. This is best explained by:

Random mutation in every individual simultaneously
Lamarckian inheritance of acquired resistance
Gene flow from a resistant population
Natural selection acting on pre-existing genetic variation (Correct answer)

Correct answer: Natural selection acting on pre-existing genetic variation

Pre-existing genetic variation for resistance allows individuals carrying resistance alleles to survive and reproduce, shifting allele frequencies via natural selection.

Question 17: Which of the following is NOT a condition required for Hardy-Weinberg equilibrium?

High mutation rate (Correct answer)
Random mating
No natural selection
Large population size

Correct answer: High mutation rate

Hardy-Weinberg equilibrium requires no mutation, no selection, random mating, no gene flow, and a large population; a high mutation rate violates the no-mutation assumption.

Question 18: Which process allows bacteria to rapidly acquire new genes, including antibiotic resistance genes, from other bacteria?

Mitosis
Meiosis
Translation
Horizontal gene transfer (Correct answer)

Correct answer: Horizontal gene transfer

Horizontal gene transfer, including conjugation, transformation, and transduction, allows bacteria to acquire genes from other organisms outside of vertical inheritance.

Question 19: What is the central dogma of molecular biology?

DNA → Protein → RNA
Protein → RNA → DNA
DNA → RNA → Protein (Correct answer)
RNA → DNA → Protein

Correct answer: DNA → RNA → Protein

The central dogma describes the flow of genetic information: DNA is transcribed into RNA, which is then translated into protein.

Question 20: What is a frameshift mutation?

A point mutation that changes one amino acid
An insertion or deletion that alters the reading frame (Correct answer)
A mutation that creates a premature stop codon
A chromosomal inversion

Correct answer: An insertion or deletion that alters the reading frame

Frameshift mutations result from insertions or deletions of nucleotides that are not multiples of three, disrupting the reading frame.

Question 21: In population ecology, what does the logistic growth model add to the exponential growth model?

Carrying capacity (K) (Correct answer)
Age structure
Immigration and emigration rates
Predation pressure

Correct answer: Carrying capacity (K)

The logistic model incorporates carrying capacity (K), limiting population growth as resources become scarce and population size approaches the environmental maximum.

Question 22: Which concept describes the variety of species, genetic diversity, and ecosystem types within a region?

Ecological succession
Biodiversity (Correct answer)
Niche differentiation
Trophic efficiency

Correct answer: Biodiversity

Biodiversity encompasses species diversity, genetic diversity, and ecosystem diversity, and is a key indicator of ecosystem health and resilience.

Question 23: Which ecological concept describes the role and position a species occupies in its environment, including its habitat and interactions?

Ecological niche (Correct answer)
Trophic level
Carrying capacity
Biome

Correct answer: Ecological niche

An ecological niche encompasses all the biotic and abiotic conditions a species needs to survive and reproduce, including its functional role.

Question 24: What term describes species that arrive early in ecological succession and modify the environment for later species?

Indicator species
Pioneer species (Correct answer)
Keystone species
Climax species

Correct answer: Pioneer species

Pioneer species colonize barren or disturbed habitats first, altering soil and microclimate to allow subsequent species to establish.

Question 25: In the Hardy-Weinberg equilibrium model, which condition would cause allele frequencies to change over time?

No migration
Natural selection (Correct answer)
Large population size
Random mating

Correct answer: Natural selection

Natural selection causes differential reproductive success based on phenotype, which shifts allele frequencies and violates Hardy-Weinberg equilibrium.

Biology Test Practice Test: Video 1 Answers (25 Questions)

Which cytoskeletal element is primarily responsible for maintaining cell shape in animal cells?

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