Praxis 5005

Which boundary marks the sudden increase in seismic wave velocities between the Earth's crust and mantle?

• The lithosphere
• The asthenosphere
• The Mohorovičić discontinuity (Moho)
• The Gutenberg discontinuity

Answer explanation

The Mohorovičić discontinuity, or Moho, is the boundary where seismic waves speed up dramatically, marking the transition from the crust to the mantle.

What is the primary driver behind Earth’s weather systems?

• Plate tectonics
• Solar radiation
• Gravitational forces from the Moon
• Geothermal heat

Answer explanation

Solar radiation heats the Earth's surface unevenly, creating temperature differences that drive atmospheric circulation and weather patterns.

Which phenomenon best explains the apparent daily movement of stars across the night sky?

• The Earth’s orbit around the Sun
• The tilt of the Earth’s axis
• The Earth’s rotation on its axis
• The precession of the equinoxes

Answer explanation

The Earth's rotation on its axis causes the stars to appear to move across the sky throughout the night.

Which type of rock is formed by the cooling and solidification of magma?

• Sedimentary rock
• Metamorphic rock
• Igneous rock
• Fossiliferous rock

Answer explanation

Igneous rocks form when molten magma or lava cools and solidifies, either beneath or on the Earth’s surface.

A tsunami is most commonly triggered by:

• Strong coastal winds
• Underwater volcanic eruptions
• Large-scale oceanic temperature changes
• Underwater earthquakes

Answer explanation

Underwater earthquakes can displace large volumes of water, causing tsunamis that travel across the ocean.

Which organelle is primarily responsible for producing ATP in eukaryotic cells?

• Chloroplast
• Nucleus
• Mitochondrion
• Endoplasmic reticulum

Answer explanation

Mitochondria generate ATP through cellular respiration, making them the cell’s powerhouse.

A homozygous genotype is characterized by:

• Two different alleles for a gene
• A mutation in one allele
• The complete absence of a gene
• Two identical alleles for a gene

Answer explanation

A homozygous genotype means that an individual has two identical alleles for a specific gene.

Which process in sexually reproducing organisms is responsible for genetic variation?

• Mitosis
• Meiosis
• Binary fission
• Budding

Answer explanation

Meiosis introduces genetic variation through mechanisms such as crossing over and independent assortment during gamete formation.

Natural selection is best described as:

• The process by which advantageous traits become more common over time
• The random mutation of genes
• The elimination of all genetic variation
• The process of gene flow between populations

Answer explanation

Natural selection favors traits that increase survival and reproductive success, gradually shifting allele frequencies.

What defines an ecosystem?

• A group of organisms sharing common ancestry
• A system where organisms do not interact
• A community of living organisms interacting with their physical environment
• A collection of non-living chemical elements

Answer explanation

An ecosystem consists of living organisms interacting with non-living environmental factors in a defined area.