Mixed Deck — All SAT Topics Flashcards

Which hormone regulates blood sugar?

Answer: Insulin

Insulin is a vital hormone produced by the pancreas that plays a central role in regulating blood glucose (sugar) levels. After a meal, when blood sugar rises, insulin signals cells to absorb glucose from the bloodstream for energy or storage. This action effectively lowers blood sugar, maintaining the body's internal balance.

In the coastal kelp forest ecosystems of the North Pacific, sea otters prey on sea urchins. Sea urchins, if left unchecked, will graze voraciously on kelp, destroying the forests that provide habitat for numerous other species. The sea otter's role in maintaining the structure of this community is best described as that of a(n):

Answer: Keystone species

A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance. By controlling the sea urchin population, sea otters prevent the destruction of kelp forests and thereby maintain the entire community's structure and biodiversity. [4, 13, 18, 22] While they are also apex predators, the term "keystone species" specifically describes this critical ecological role.

A human cell with 46 chromosomes undergoes meiosis. How many chromosomes will each resulting cell contain?

Answer: 23

Meiosis halves the chromosome number, so a diploid cell with 46 chromosomes produces haploid cells with 23 chromosomes.

Which of the following describes the primary role of calcium ions (Ca2+) in the contraction of a skeletal muscle fiber?

Answer: To bind to troponin, which causes tropomyosin to shift and expose the myosin-binding sites on actin.

In skeletal muscle contraction, an action potential triggers the release of Ca2+ from the sarcoplasmic reticulum. These calcium ions then bind to troponin, a protein complex on the actin filament. This binding causes a conformational change that moves the tropomyosin protein, uncovering the sites on actin where myosin heads can bind, thus initiating the cross-bridge cycle and muscle contraction.

Which phase of meiosis most closely resembles mitosis because sister chromatids (not homologs) separate?

Answer: Meiosis II

Meiosis II resembles mitosis in that sister chromatids separate (rather than homologs), though the cells entering meiosis II are already haploid.

DNA replication occurs during which phase of the cell cycle?

Answer: S phase

DNA synthesis (replication) occurs exclusively during the S (synthesis) phase of interphase.

During the transmission of a nerve impulse, the rapid depolarization of the neuron's membrane is primarily caused by which event?

Answer: The influx of sodium ions (Na+).

When a neuron reaches its threshold potential, voltage-gated sodium channels open rapidly. This allows a massive influx of positively charged sodium ions (Na+) to rush into the cell, down their electrochemical gradient. This rapid influx of positive charge causes the membrane potential to shoot up from negative to positive, an event known as depolarization, which is the rising phase of the action potential.

Which scientist is known for the theory of evolution by natural selection?

Answer: Charles Darwin

Charles Darwin is widely recognized for his groundbreaking work on the theory of evolution by natural selection, published in "On the Origin of Species." His theory proposed that species evolve over time through a process where individuals with advantageous traits are more likely to survive and reproduce. This concept revolutionized biology and our understanding of life's diversity.

A small group of individuals colonizes a new island. The allele frequencies of this new population are, by chance, very different from the original population. This phenomenon is known as:

Answer: The founder effect

The founder effect is a form of genetic drift that occurs when a new population is established by a small number of individuals whose gene pool differs from that of the source population. This random sampling can lead to a new population with non-representative allele frequencies compared to the original population.

Which of the following correctly describes the order of phases in mitosis?

Answer: Prophase, Metaphase, Anaphase, Telophase

The correct order of mitotic phases is Prophase, Metaphase, Anaphase, and Telophase, remembered by the mnemonic PMAT.

What is the primary function of ribosomes?

Answer: Protein synthesis

Ribosomes are cellular organelles responsible for protein synthesis, a process also known as translation. They read the genetic information encoded in messenger RNA (mRNA) and use it to assemble amino acids into specific protein sequences. This function is vital for all cellular activities, as proteins perform a vast array of functions within the cell and organism.

What term describes a change in DNA sequence?

Answer: Mutation

A mutation is a permanent alteration in the DNA sequence that makes up a gene or chromosome. These changes can range from a single nucleotide substitution to large-scale chromosomal rearrangements. Mutations are the ultimate source of genetic variation, which is essential for evolution, though they can also be harmful.

Which organ system controls body responses?

Answer: Nervous system

The nervous system, consisting of the brain, spinal cord, and nerves, is the body's primary control and communication system. It detects stimuli, processes information, and coordinates rapid responses to both internal and external changes. This system enables thought, movement, sensation, and the regulation of vital bodily functions.

A man with type AB blood and a woman with type O blood have a child. What is the probability that their child will have type A blood?

Answer: 50%

The man's genotype is I^A I^B, and the woman's genotype is ii. The possible genotypes for their offspring are I^A i (Type A blood) and I^B i (Type B blood). Therefore, there is a 50% chance of having a child with type A blood and a 50% chance of having a child with type B blood.

A scientist designs an experiment to measure the rate of photosynthesis in a green alga. She places the alga in a sealed container with a buffered solution and a light source. Which of the following environmental changes would most likely lead to an increase in the rate of O2 production?

Answer: Increasing the intensity of the white light.

The rate of photosynthesis is limited by factors such as light intensity, CO2 concentration, and temperature. Increasing the intensity of white light provides more energy for the light-dependent reactions, thus increasing the rate of water splitting and O2 production, up to a certain saturation point. [12] Decreasing CO2 would limit the Calvin cycle, and green light is largely reflected by chlorophyll, making it ineffective for photosynthesis.

What is the primary source of energy in most ecosystems?

Answer: The Sun

The Sun is the fundamental source of energy for nearly all ecosystems on Earth. Through the process of photosynthesis, producers like plants and algae capture solar energy and convert it into chemical energy in the form of organic compounds. This stored energy then forms the base of the food web, making it available to all other organisms in the ecosystem.

Which of the following statements correctly describes a key difference between the leading and lagging strands during DNA synthesis?

Answer: The lagging strand is synthesized as a series of Okazaki fragments, while the leading strand is synthesized continuously.

Because DNA polymerase can only add nucleotides to the 3' end of a growing strand, synthesis must always proceed in the 5' to 3' direction. The leading strand is synthesized continuously towards the replication fork. The lagging strand, however, is synthesized discontinuously away from the replication fork in short pieces called Okazaki fragments, which are later joined together.

Which of the following correctly traces the path of deoxygenated blood as it enters the heart and is pumped toward the lungs?

Answer: Superior Vena Cava → Right Atrium → Right Ventricle → Pulmonary Artery

Deoxygenated blood from the systemic circuit returns to the heart via the superior and inferior vena cavae, entering the right atrium. From there, it passes through the tricuspid valve into the right ventricle. The right ventricle then contracts, pumping the deoxygenated blood through the pulmonary valve into the pulmonary artery, which carries it to the lungs for oxygenation.

Which of the following enzymes is responsible for unwinding the DNA double helix during replication?

Answer: Helicase

Helicase is the enzyme that separates the two strands of the DNA double helix by breaking the hydrogen bonds between complementary base pairs, creating the replication fork. DNA Polymerase synthesizes new DNA strands, DNA Ligase joins DNA fragments, and Primase synthesizes RNA primers.

What behavior is learned through experience?

Answer: Learned behavior

Learned behavior is any behavior acquired or modified through an organism's experiences, observations, or practice during its lifetime. Unlike innate behaviors (reflexes or instincts) which are genetically programmed, learned behaviors allow organisms to adapt to new situations and environments. Examples include training a pet or a child learning to speak.