The Ultimate Biology Gauntlet: Are You a True Biologist? #4

Pepsin is a digestive enzyme that specifically breaks down proteins into smaller peptides. Options a, c, and d describe functions associated with other digestive enzymes or processes.

The small intestine is the primary site for nutrient absorption due to its extensive surface area with villi and microvilli. This efficient absorption process ensures essential nutrients are assimilated into the bloodstream for various metabolic functions. Options a, c, and d are associated with other digestive or metabolic functions. The stomach initiates protein digestion, the large intestine focuses on water absorption, and the liver contributes to metabolic processes but is not a site for nutrient absorption.

Insects belong to the phylum Arthropoda, which is characterized by segmented bodies and exoskeletons made of chitin. This diverse phylum includes not only insects but also arachnids, crustaceans, and myriapods. Options a, c, and d correspond to other animal phyla--Mollusca, Chordata, and Annelida, respectively--each with distinct characteristics such as soft bodies, notochords, or segmented worms, setting them apart from insects in the animal kingdom.

Glucose is a monosaccharide, representing the simplest form of sugar, consisting of a single sugar unit. Options b, c, and d, on the other hand, are examples of disaccharides--sucrose, lactose, and maltose--each composed of two sugar molecules through chemical bonding.

Lysosomes contain digestive enzymes and are responsible for breaking down cellular waste, damaged organelles, and foreign materials. While other organelles contribute to cellular functions, none specialize in the recycling process like lysosomes.

Mitochondria are the site of respiration in animal (and plant) cells. Cells which need more energy like muscle cells, have more mitochondria. The cytoplasm is a jelly-like material where many chemical reactions occur. The nucleus contains genetic material, including DNA, which controls the cell’s activities. Ribosomes are the site of protein synthesis (where proteins are made). The cell membrane surrounds the cell and controls what enters and leaves it.

The villi in the digestive system is the correct example of exchange surfaces with a large surface area. The elongated (long length) axons in neurones helps impulses pass along them quickly. These are not exchange surfaces. The flagella of some bacteria allow them to move. These are not exchange surfaces. The ciliated cells lining oviduct have tiny hairs (cilia) which beat regularly to move the egg from the ovary to the uterus. These are not exchange surfaces.

The correct answer is that many farmers believe that tuberculosis is spread by badgers to their cows. Organisms that spread communicable diseases are called vectors. The malaria mosquito transmits this disease from the blood of infected people to those that are not infected. Direct contact transmits some communicable diseases between people, but not tuberculosis. Direct contact can be sexual or non-sexual touching. Untreated water can transmit many diseases, such as the cholera bacterium but again not tuberculosis. Coughs and sneezes can transmit communicable diseases like the common cold through the air. Their tiny droplets can contain viruses which can infect those that breathe them in.

Amino acids are the substances that are made by joining glucose and nitrates from the soil. Amino acids are the building blocks of proteins which are made when they join together in the correct sequence. Lipids are fats (solid at room temperature) and oils (liquids under the same conditions). Glucose is stored as lipids in plant seeds. We make sunflower oil from sunflower seeds. Many molecules of glucose made in photosynthesis are joined together to make starch which is a storage form of carbohydrate found in rice, cereals and potatoes. Many molecules of glucose are joined together to make cellulose, which is used to make cells walls. Cellulose provides the strength for plant cells.

Receptor cells detect stimuli, which are changes in the environment. You have receptors in all of your sense organs, and temperature, pressure and pain receptors in your skin. They detect changes and send electrical signals along nerves to your brain. Effectors are muscles or glands at the end of your motor neurones. They respond to signals sent from your central nervous system. Muscles move parts of your body, and glands release hormones (which are chemical signals) into your blood. Synapses are gaps between neurones where chemicals called neurotransmitters move quickly by diffusion to start the electrical signal again in the next neurone. Nerves are made from bundles of individual neurone cells

The stages of mitosis in which chromosomes and their copies line up in the middle of a cell is called metaphase. The first stage in mitosis is for the DNA in the cell, which is arranged into chromosomes, to condense and become more visible. This occurs in prophase, where the membrane around the nucleus also disappears. Metaphase is the next stage. After this comes anaphase, where chromosomes and their copies are pulled towards the ends (poles) of the cell, so it can split into two. Telophase happens before this when new membranes form around the chromosomes at each end of the cells. Finally the cell splits into two genetically identical cells during cytokinesis.

Competition for resources between individuals of the same species is called intraspecific. ‘Intra’ in science means ‘within’ so this competition is within one species. The correct example is therefore young oak trees (one species) seeking light under their parent tree. Competition for resources between individuals of different species is called interspecific. ‘Inter’ in science means ‘between’ so this competition is between different species. Examples of this are zebras and gazelle (different species) grazing on grass, magpies and red kites (different species) feeding on roadkill, and rats and mice (different species) eating grain.

It is the objective lenses that can easily be changed to alter the magnification. The highest magnification objective lens is often x40. The eyepiece lens cannot easily be changed. This is often x10 on a light microscope. The condenser ensures light is spread uniformly over the slide you are looking at. The coarse focus allows you to quickly find near to the perfect focus, which you can then find using the fine focus.

The box jellyfish is also called the sea wasp and occurs widely from Queensland northward to Malaysia. It is dangerously venomous; a sting can cause death within a few minutes.