Science: Life Science Practice Test Flashcards

Which organelle is responsible for producing ATP through cellular respiration in eukaryotic cells?

Answer: Mitochondria

Mitochondria are the powerhouses of the cell, generating ATP through aerobic cellular respiration via the Krebs cycle and electron transport chain.

Which process do plants use to convert light energy into chemical energy stored in glucose?

Answer: Photosynthesis

Photosynthesis uses light energy, water, and carbon dioxide to produce glucose and oxygen, occurring primarily in chloroplasts.

What is the term for the process by which a cell divides to produce two genetically identical daughter cells?

Answer: Mitosis

Mitosis is the cell division process in eukaryotes that produces two genetically identical diploid daughter cells, used for growth and tissue repair.

Which type of molecule carries the genetic instructions from the nucleus to the ribosomes?

Answer: mRNA

Messenger RNA (mRNA) carries the genetic code transcribed from DNA in the nucleus to the ribosomes in the cytoplasm, where it serves as a template for protein synthesis.

In Mendel's experiments, what term describes a trait that is hidden when a dominant trait is present?

Answer: Recessive

A recessive trait is masked when a dominant allele is present. It only shows in an individual who inherits two copies of the recessive allele (homozygous recessive).

Which level of biological organization is directly above the organ level?

Answer: Organ system

The organ system level is directly above the organ level. Organs work together in organ systems (e.g., the heart and blood vessels form the cardiovascular system).

What is the primary role of decomposers in an ecosystem?

Answer: Breaking down dead organic matter into nutrients

Decomposers break down dead organisms and organic waste, recycling nutrients back into the soil and making them available for producers.

Which structure controls what enters and exits a cell, maintaining homeostasis?

Answer: Cell membrane

The cell membrane (plasma membrane) is selectively permeable, regulating the passage of substances into and out of the cell to maintain homeostasis.

According to Darwin's theory of natural selection, which individuals in a population are most likely to survive and reproduce?

Answer: Those with traits best suited to the environment

Natural selection favors individuals with traits that improve survival and reproduction in a given environment, leading to those traits becoming more common over generations.

What type of symbiosis describes a relationship where one organism benefits and the other is neither harmed nor helped?

Answer: Commensalism

Commensalism is a symbiotic relationship where one organism benefits and the other is unaffected. An example is barnacles living on whales.

Which base pairs with adenine in a DNA double helix?

Answer: Thymine

In DNA, adenine (A) pairs with thymine (T) via two hydrogen bonds, and guanine (G) pairs with cytosine (C) via three hydrogen bonds.

What is the term for an organism's full genetic makeup, including all alleles?

Answer: Genotype

An organism's genotype is its complete set of genetic instructions (alleles), which determines its inherited traits. The phenotype is the observable expression of those genes.

In an ecosystem's food chain, organisms that make their own food using sunlight are called:

Answer: Producers

Producers (autotrophs) make their own food through photosynthesis or chemosynthesis. They are the foundation of every food chain, providing energy for all other organisms.

Which process moves water from soil into a plant's roots by osmosis?

Answer: Osmosis driven by a concentration gradient

Water moves into root cells by osmosis — from an area of high water concentration (the soil) to an area of lower water concentration (the root cells with dissolved solutes).

What is the function of the large intestine in the human digestive system?

Answer: Absorbing water and forming solid waste

The large intestine primarily absorbs water and electrolytes from indigestible food matter, forming solid feces for elimination.

Which of the following BEST describes a niche in ecology?

Answer: The role and position of an organism in its ecosystem

An ecological niche encompasses the role an organism plays in its ecosystem, including its interactions, diet, behavior, and adaptations — not just its location (habitat).

What happens to energy as it flows from one trophic level to the next in a food chain?

Answer: Approximately 90% of energy is lost as heat at each level

About 90% of energy is lost as heat (through metabolism and waste) at each trophic level, meaning only ~10% is available to the next level.

What type of cell division produces gametes (sperm and egg cells) with half the normal chromosome number?

Answer: Meiosis

Meiosis reduces the chromosome number by half (from diploid to haploid), producing four genetically unique gametes. When two gametes fuse at fertilization, the diploid number is restored.

Which of the following is evidence of evolution?

Answer: Homologous structures in different species suggest a common ancestor

Homologous structures — anatomically similar body parts in different species (e.g., the human arm, whale flipper, and bat wing) — suggest descent from a common ancestor and support evolution.

What is the role of ribosomes in a cell?

Answer: Synthesizing proteins

Ribosomes are the sites of protein synthesis (translation), where the mRNA sequence is decoded to assemble a chain of amino acids into a polypeptide.