Correct Answer: (4) It obtains nutrients from its environment.

Heterotrophs are organisms that obtain organic food molecules by eating other organisms or their by-products, unlike autotrophs, which can produce their own food by converting light energy from the sun into chemical energy through photosynthesis. Mushroom spores grow on their food (e.g. wood, soil), from which they absorb organic matter to derive energy.

Incorrect Answers:

(1)   It manufactures its own food.

Mushrooms produce food by absorbing organic matter from their substrate to obtain energy. It cannot produce food on its own unlike plants and algae that gather light energy and transform it into chemical energy through photosynthesis. Organisms that can produce their own food are called autotrophs.

(2)   It divides by mitosis.

Heterotrophic refers to a characteristic of organisms that function through a certain mode of nutrition wherein they obtain energy by absorbing nutrients from living or dead matter. On the other hand, mitosis is a type of cell division wherein the chromosome number of the offspring is the same with their parents'. The type of cell division has no direct link on the mode of nutrition of organisms.

(3)   It transforms light energy into chemical energy,

Correct Answer: (2) protein

Meat is composed of proteins. When proteins are ingested, the initial digestion occurs in the stomach, where the protein is converted into small polypeptides with the help of an enzyme called pepsin. Then the protein goes to the small intestines, where most of the digestion process occurs. The small polypeptides are further broken down into smaller polypeptides with the help of the enzymes trypsin and chymotrypsin. Then these polypeptides are again broken down into amino acids, which are highly complex organic compounds. Digestion of meat takes around 30 minutes to less than a day, depending on several factors such as type of meat and rate of metabolism of the individual. After three days, the meat protein will have been converted to amino acids, and then distributed to different parts of the body; some of the amino acids are again formed into proteins to perform specific functions inside the body.

Incorrect Answers:

(1) glucose

There are four types of macrobiomolecules: protein, carbohydrate, nucleic acid, and fat. Each of these undergoes different pathways of digestion. Since meat is composed mostly of protein, then the product of meat digestion is amino acid or protein (after three days). Glucose is a simple sugar produced from carbohydrates, which is different from proteins.

(3) starch

Starch is a polysaccharide. In the initial stage of digesting carbohydrates, they are broken down inside the oral cavity into simpler and smaller polysaccharides like maltose. Proteins cannot be converted into complex sugars like starch.

(4) oxygen

Oxygen enters the body through respiration and distributed through the circulation of blood. It is not a product of meat digestion.

Correct Answer: (3) circulatory-transports materials for energy release in body cells

The circulatory system transports nutrients, gases, hormones, blood cells, nitrogen waste products, from cell to cell of the body to help fight diseases, help stabilize body temperature and pH to maintain homeostasis.

Incorrect Answers:

(1) excretory-produces antibodies to fight disease-causing organisms

The excretory system is involved in the disposal of nitrogen-containing waste products of metabolism. The immune system composed of special cells, proteins, tissues, and organs, is responsible for the formation of antibodies and defense against disease.

(2) digestive-produces hormones for storage and insulation

The digestive system is the organ system involved in the breaking down of food into molecules small enough for the body to absorb. It is the endocrine system that is involved in the production of hormones for storage and insulation.

(4) respiratory-collects waste material for digestion

The respiratory system is responsible for oxygenation of blood to be distributed to the different parts of the body. The excretory system is the organ system in charge of the elimination of the waste products of metabolism.

A hormone is a chemical signal secreted into body fluids (like blood) by specialized cells. A certain hormone may reach all parts of the body but only specific types of cells called target cells which are equipped to react with them. When the target cells recognize the presence of the hormone, they bind to receptor proteins located in the cytoplasm and/or nucleus. This now forms the hormone-receptor complex that binds to particular sequences of DNA serving as transcription factors regulating a particular response.

(1)These cells have different DNA than the cells in other body systems.

Deoxyribonucleic acid (DNA) carries all the genetic instructions for the development and functioning of organ. Though it is true that the cells in the sex cells are different from the rest of the body cells, this does not directly affect the cell-hormone relationship.

(3) Reproductive system cells could be harmed if they made contact with hormones from other body systems.

Non-target reproductive cells are not affected by the hormones because of the absence of receptors. When the receptors are absent, the hormone cannot bind with the cell and cause any positive or negative reaction.

(4) Cells associated with the female reproductive system only respond to the hormone testosterone.

Testosterone, a predominant androgen hormone in the male body, is just one among a number of hormones present in the human body. And just like any other hormone, testosterone only affects its target cells, which are most found in the male body.

The structure B is the plasma membrane. It is a semi-permeable membrane at the boundary of every cell that acts as a selective barrier, thereby regulating the entrance of materials and exit of wastes in the cell.  The waste products move out of the cell usually through osmosis.

(1) A

This is the nucleus. It is the organelle that contains the genetic material of the plant cell.

(3) C

These structures are called vacuoles, which store food, water, minerals, and wastes. In plant cells, vacuoles are larger to contribute in the rigidity of the cell.

(4) D

D illustrates the mitochondrion (mitochondria, plural) or the powerhouse of the cell. It is responsible for the release of energy for all the cellular functions.

The vacuole is a membrane-enclosed cell organelle that is responsible for the storage of water, food, minerals, and waste in the cell.

Incorrect Answers:

(2) coordination

The nucleus is known as the control center of all activities of the cell. Hence, it is responsible for coordination.

(3) synthesis of molecules

Ribosome, a cell organelle constructed in the nucleolus, is the site of protein synthesis in the cytoplasm.

(4) release of energy

It is the center of cell respiration, thus it is regarded as the powerhouse of the cell and responsible for releasing energy for all cell functions.

In the DNA, the purine bases are adenine (A) and guanine (G), while the pyrimidine bases are thymine (T) and cytosine (C). According to Chargaff's rule, the DNA from any cell of all organisms should have a 1:1 ratio of pyrimidine and purine bases. Thus, %A = %T and %G = %C. Thus, if the DNA sample has 15% T, then it must also contain 15% A. The A-T pair already constitutes 30%, and thus the G-C pair would make up the 70%. Since G is equal to C, then simply divide 70% by 2, then you will get the C% which is 35.

Incorrect Answers:

(1) 15%

(3) 70%

(4) 85 %

All the other options are incorrect because they do not follow the Chargaff's rule of base pairing.

Global warming refers to the phenomenon characterized by the increase in the average temperature of the earth. The primary cause of global warming is the accumulation of greenhouse gases due to human activities such as deforestation and burning of fossil fuels. The increased temperature leads to the melting of ice caps. Thus, global warming contributed to the decrease in the sizes of polar ice caps.

Incorrect Answers:

(2) temperature of Earth

When global warming occurs, the temperature of the earth increases or the surrounding becomes hotter than the usual temperature.

(3) rate of species extinction

Since there is unusually high temperature during global warming, some species cannot adapt to the change of temperature. When the species fail to thrive and all of them are wiped out, the species become extinct. This leads to the increase (not decrease) of the rate of species extinction.

(4) rate of carbon dioxide production

The increase in the concentration of carbon dioxide in the atmosphere is a consequence of combustion of fossil fuels and burning large quantities of wood. The high concentration of carbon dioxide in the atmosphere causes interception and absorption of the reflected infrared radiation, rereflecting it back to the Earth. Thus, solar heat is retained inside the Earth's surface and atmosphere. This phenomenon is known as the greenhouse effect.

Genetic information is contained in the DNA. All DNAs in the body cells are the same, thus, all the structures indicated-skin, eyes and leg muscles-all have identical genetic information.

Incorrect Answers:

(1) equal amounts of ATP

Adenosine triphosphate (ATP) is an adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. Since ATP is the energy currency of the body, there are more ATP found in the leg muscles because they are used for movement compared to those found in the skin and eyes, which both need less amount of energy to function.

(3) proteins that are all identical

The pointed structures are made up proteins. However, these proteins are not the same in all parts because they are arranged and synthesized in a specific manner depending on the function of the body parts. Since the eye, skin, and leg muscles have different functions, thus they are composed of different proteins.

(4) organelles for the synthesis of glucose

Evolution refers to the changes that have transformed life on Earth from its earliest beginnings to the diversity that characterizes it today. There are five possible causes of evolution: natural selection, genetic drift, mutation, gene flow, and nonrandom mating. When an organism is isolated from the rest of the population and is able to reproduce in the new location, natural selection can occur and cause evolution. The species could have evolved due to its adaptation to the new environment.

Incorrect Answers:

(2) is due to a genetic code that is present in the gametes of the organism

Evolution could not occur because the genetic code is still present in the gametes of the organism. Thus, there is no change in species' genome.

(3) decreases the number of gene in the body cells of the organism

Genetic changes such as mutation in the body cells are not carried on to the next generation because they do not give rise to gametes. Thus, a change in the numbers of genes in the body cells could not cause evolution of species.

(4) causes a change in the environment surrounding the organism