MTEL Science Content Knowledge 2 — Questions and Answers
Question 1: What distinguishes a physical change from a chemical change in matter?
- A physical change involves a color change; a chemical change does not
- In a physical change the composition of the substance remains the same; in a chemical change a new substance with different properties is formed (Correct answer)
- Physical changes are reversible; chemical changes always are not
- Physical changes involve solids; chemical changes involve liquids
Correct answer: In a physical change the composition of the substance remains the same; in a chemical change a new substance with different properties is formed
Physical changes alter the form or appearance of matter without changing its chemical composition, while chemical changes produce new substances with different properties.
In a physical change (tearing paper, melting ice, dissolving salt), no new substance is created. In a chemical change (burning wood, rusting iron, baking a cake), new substances form with different properties. Evidence of chemical change includes gas production, color change, heat/light release, and formation of a precipitate.
Question 2: What is the role of decomposers in an ecosystem?
- They produce organic matter through photosynthesis
- They consume other living organisms for energy
- They break down dead organic matter, recycling nutrients back into the ecosystem (Correct answer)
- They regulate the population of primary consumers
Correct answer: They break down dead organic matter, recycling nutrients back into the ecosystem
Decomposers (fungi and bacteria) break down dead organisms and waste products, releasing nutrients back into the soil and water where they become available to producers.
Decomposers are essential links in biogeochemical cycles. Without them, nutrients locked in dead organic matter would not be recycled. Fungi and bacteria are the primary decomposers in most ecosystems. They release carbon, nitrogen, phosphorus, and other nutrients back into the abiotic environment. This connects to carbon and nitrogen cycle content in Massachusetts life science standards.
Question 3: What is the difference between a food chain and a food web in ecology?
- A food chain shows one linear feeding sequence; a food web shows multiple interconnected feeding relationships in an ecosystem (Correct answer)
- A food chain applies to marine ecosystems; a food web applies to terrestrial ecosystems
- A food chain is more accurate than a food web for representing energy flow
- A food web shows only predator-prey relationships; a food chain shows all ecological relationships
Correct answer: A food chain shows one linear feeding sequence; a food web shows multiple interconnected feeding relationships in an ecosystem
A food chain shows a single linear sequence of who eats whom, while a food web depicts the complex network of all feeding relationships within an ecosystem.
Food chains represent single, linear pathways of energy transfer. Food webs are more ecologically accurate, showing that most organisms eat and are eaten by multiple species. The interconnected nature of food webs means that removing one species can have cascading effects known as a trophic cascade. Massachusetts life science standards emphasize food webs as more realistic models of ecosystem energy flow.
Question 4: Which of the following describes the process of natural selection as proposed by Charles Darwin?
- Organisms intentionally change their traits to better survive in their environment
- Individuals with heritable traits better suited to their environment tend to survive and reproduce more successfully, passing those traits to offspring (Correct answer)
- All members of a species change their traits simultaneously in response to environmental pressure
- Traits acquired during an organism lifetime are passed on to offspring
Correct answer: Individuals with heritable traits better suited to their environment tend to survive and reproduce more successfully, passing those traits to offspring
Natural selection occurs when heritable variations that increase fitness lead to greater reproductive success, causing those traits to become more prevalent in a population over generations.
Darwin theory of natural selection has four key components: variation (individuals differ), heritability (traits are passed to offspring), differential reproduction (some individuals survive and reproduce better), and selection (environment determines which traits are advantageous). Natural selection acts on existing variation and does not intentionally direct change. Evolution by natural selection is foundational life science content for MTEL biology candidates.
Question 5: What is the difference between an element and a compound in chemistry?
- An element contains multiple types of atoms; a compound contains only one type
- An element consists of one type of atom; a compound consists of two or more elements chemically bonded together (Correct answer)
- An element is a liquid; a compound is a solid
- An element can be broken down by heating; a compound cannot
Correct answer: An element consists of one type of atom; a compound consists of two or more elements chemically bonded together
An element is a pure substance consisting of only one type of atom. A compound is a substance formed when two or more elements are chemically bonded in a fixed ratio.
Elements are the simplest chemical substances listed on the periodic table. Compounds are formed through chemical bonds between two or more different elements in fixed ratios. Compounds have properties distinct from their component elements: sodium plus chlorine forms sodium chloride (table salt). Mixtures differ from compounds in that components are not chemically bonded and can be separated by physical means.
Question 6: What is the primary function of the mitochondria in a eukaryotic cell?
- Synthesizing proteins from amino acids
- Controlling cell division and reproduction
- Producing energy (ATP) through cellular respiration (Correct answer)
- Manufacturing and transporting lipids and proteins
Correct answer: Producing energy (ATP) through cellular respiration
Mitochondria are the sites of cellular respiration, where glucose and oxygen are converted to ATP (adenosine triphosphate), the cell primary energy currency.
Cellular respiration occurs in three main stages: glycolysis (cytoplasm), the Krebs cycle (mitochondrial matrix), and the electron transport chain (inner mitochondrial membrane). The net result is the production of up to 36-38 ATP molecules per glucose molecule. Mitochondria have their own circular DNA, supporting the endosymbiotic theory of their origin as engulfed bacteria.
MTEL Science Content Knowledge 2
What distinguishes a physical change from a chemical change in matter?