Regents Examination in Living Environment: Questions on Standard 4, Biological Concepts, Key Idea 5 - Dynamic Equilibrium and Homeostasis

Key Idea 5—Dynamic Equilibrium and Homeostasis
Organisms maintain a dynamic equilibrium that sustains life.

Which energy conversion occurs in the process of photosynthesis?
Light energy is converted to nuclear energy.
Chemical bond energy is converted to nuclear energy.
Light energy is converted to chemical bond energy.
Mechanical energy is converted to light energy.

An environmental change that would most likely increase the rate of photosynthesis in a bean plant would be an increase in the
intensity of green light
concentration of nitrogen in the air
concentration of oxygen in the air
concentration of carbon dioxide in the air

During photosynthesis, molecules of oxygen are released as a result of the “splitting” of water molecules. This is a direct result of the
dark reaction
light reaction
formation of PGAL
formation of CO2

An organism that makes its own food without the direct need for any light energy is known as a
chemosynthetic heterotroph
chemosynthetic autotroph
photosynthetic heterotroph
photosynthetic autotroph

While looking through a microscope at a section of a leaf from a freshwater plant, a student observed some cells in which chloroplasts were moving around with the cytoplasm. This type of movement is known as
pinocytosis
synapsis
osmosis
cyclosis

By what process does carbon dioxide pass through the stomates into the leaf ?
diffusion
osmosis
respiration
pinocytosis

Two end products of aerobic respiration are
oxygen and alcohol
oxygen and water
carbon dioxide and water
carbon dioxide andoxygen

Homeostatic regulation of the body is made possible through the coordination of all body systems. This coordination is achieved mainly by
respiratory and reproductive systems
skeletal and excretory systems
nervous and endocrine systems
circulatory and digestive systems

Phenylketonuria (PKU) is an inherited condition characterized by mental retardation. The symptoms of the disorder result from an inability to synthesize a single type of
enzyme
nutrient
blood cell
brain cell

ll the children of a hemophiliac male and a normal female are normal with respect to blood clotting. However, some of their grandsons are hemophiliacs. This is an example of the pattern of hereditary known as
sex determination
sex linkage
incomplete dominance
multiple alleles

What is the total number of chromosomes in a typical body cell of a person with Down’s syndrome?
22
23
44
47


Key Idea 5—Dynamic Equilibrium and Homeostasis: Answers and Explanations

3 In the process of photosynthesis, carbon dioxide and water molecules are converted to glucose. Light is the energy source for the reaction. Light energy is transformed into the chemical bond energy of the glucose molecules.
Wrong Choices Explained:
(1), (2), (4) The Law of Conservation of Energy states that energy cannot be created or destroyed, but it can be changed from one form to another. All the choices refer to this law, but only choice (3) occurs in living organisms.
 

4 Experiments have shown that the rate of photosynthesis depends on the availability of carbon dioxide. The greater the concentration of carbon dioxide, the greater the rate of photosynthesis.
Wrong Choices Explained:
(1) Chlorophyll is a light-absorbing pigment found in chloroplasts. However, it does not absorb much of the green wavelength of light. An increase in the intensity of green light has no effect on the photosynthetic rate.
(2) Carbohydrates are the products of photosynthesis. They do not contain atoms of nitrogen. The nitrogen needed by plants comes from nitrates in the soil, not from the concentration of nitrogen in the air.
(3) Oxygen is released during photosynthesis. Therefore, the concentration of oxygen in the air has no direct effect on photosynthesis.
 

2 Sunlight provides the energy needed to split water molecules into hydrogen and oxygen. Because light is required, this part of photosynthesis is known as the light reaction.
Wrong Choices Explained:
(1) The dark reaction does not use light energy. In this reaction, the hydrogen released from the light reaction is combined with carbon dioxide.
(3) PGAL, phosphoglyceric aldehyde, is the first stable compound formed during the dark reaction. This compound is later converted to glucose.
(4) Carbon dioxide is not formed but is used during photosynthesis.
 

2 An autotroph manufactures its own food. A chemosynthetic autotroph produces its own food without the use of light energy. It obtains its energy from certain chemical reactions that take place in the cell.
Wrong Choices Explained:
(1) A chemosynthetic organism cannot be a heterotroph. Heterotrophs do not have the ability to manufacture their own food. All animals are heterotrophs.
(3) Photosynthetic organisms manufacture their own food. They cannot be heterotrophs.
(4) A photosynthetic autotroph utilizes light energy. All green plants are photosynthetic autotrophs.
 

4 The movement of chloroplasts in the plant cell was due to the movement of cytoplasm in the cell. Cyclosis is the streaming of cytoplasm in a cell.
Wrong Choices Explained:
(1) Pinocytosis is the formation of a pocket by an infolding of the cell membrane. Large molecules are brought into the cell by this process.
(2) Synapsis is the pairing of homologous chromosomes during meiosis.
(3) Osmosis is the movement of water across a selectively permeable membrane. Osmosis is the diffusion of water.
 

1 Carbon dioxide passes through the stomates of a leaf by diffusion. Diffusion is passive transport. Molecules move along a concentration gradient from an area of high density to an area of lower density.
Wrong Choices Explained:
(2) Osmosis is the diffusion of water.
(3) Respiration is an energy-releasing process.
(4) Pinocytosis is active transport. Cells use energy to draw in large molecules by the infolding of their cell membranes.
 

3 Respiration is a process by which cells release energy from glucose molecules. Aerobic respiration requires the presence of oxygen. In the process of aerobic respiration, glucose is oxidized to carbon dioxide and water. Both compounds are end products, the results of a chemical reaction.
Wrong Choices Explained:
(1), (2), (4) All three choices are incorrect because oxygen is consumed in aerobic respiration. Oxygen is not the end product of the reaction.
 

3 Homeostasis refers to the steady state of control of the cell and, in turn, the entire body. The biochemical processes that take place in body cells occur in even and regular sequences. The cells, tissues, and organs in all body systems must function cooperatively so that the organism can carry out its life functions effectively. The coordination of all these biochemical activities is made possible by the work of the nervous and endocrine systems. The nervous system carries impulses from sense organs to the brain or spinal cord and then to effector organs such as muscles or glands. The endocrine system secretes hormones that control the functions of certain glands, tissues, and organs. Together the nervous and endocrine systems maintain the homeostasis of the body.
Wrong Choices Explained:
(1) The respiratory system is specialized for the intake and distribution of oxygen. It also expels waste gases. The reproductive system is specialized for the developing of embryos. Both systems are controlled by the nervous and endocrine systems. In mammals, hormones control gestation and birth.
(2) The skeletal system gives support to the body. Hormones control the growth of long bones. Nerve cell fibers help the muscles to function. The excretory system coordinates waste removal from the body. Hormones control water loss and reabsorption by the kidney tubules.
(4) Blood and lymph circulate by way of the circulatory system. Hydrolysis of food takes place in the digestive system. Both systems depend on the nervous and endocrine systems for the coordination of mechanical and biochemical activities.
 

1 According to the one gene–one enzyme theory, a single gene is responsible for the production of a single enzyme. Because PKU is an inherited defect, the gene for an enzyme is absent in the victim.
Wrong Choices Explained:
(2) Nutrients are not synthesized by animals. Nutrients must be taken in from organic sources.
(3) Blood cells are not affected nor involved in the PKU disorder.
(4) The development of brain cells is affected by the PKU condition. Because of the lack of an enzyme, phenylalanine is converted to phenylpyruvic acid, which accumulates in brain tissue. The result is mental retardation.
 

2 A trait that appears more often in one sex than in the other sex is said to be sex-linked. The gene for the trait is located on a sex chromosome. Hemophilia and color blindness are examples of sex-linked traits.
Wrong Choices Explained:
(1) Sex determination is controlled by a pair of sex chromosomes. There are two kinds of sex chromosomes, an X and a Y chromosome. A female has two X chromosomes (XX). A male has one X chromosome and one Y chromosome (XY).
(3) Incomplete dominance is a type of inheritance in which neither allele in a hybrid is dominant. The hybrid shows a trait completely different from either parent. The inheritance of color in a Japanese four-o’clock flower is an example of incomplete dominance, or blending.
(4) Alleles are different forms of the same gene. The term multiple alleles implies that a gene has more than two forms. Inheritance of human blood type involves multiple alleles.
 

4 The normal number of chromosomes in human body cells is 46. Down’s syndrome results from the presence of an extra chromosome. The extra or 47th chromosome is due to meiotic nondisjunction.
Wrong Choices Explained:
(1), (3) The numbers 22 and 44 do not apply to any known normal human chromosome number.
(2) The number 23 is the monoploid number of chromosomes in human gametes.