Natural Sciences 3

Anaerobic literally means without air. Biologically, this term is used to indicate no free oxygen present, that is, all oxygen atoms are tied up in chemical compounds. Free oxygen would be in the form of a gas, or dissolved in a liquid. For example, glycolysis is an anaerobic process because it does not require free oxygen, while the Krebs cycle is aerobic because it does.

Directly or indirectly, the vast bulk of organisms derive their energy from the sun. Green plants and algae are the primary producers of the ecosystem, channeling solar energy into the biosphere, and all other organisms depend on them.

The most-concentrated filtrate within the loop of Henle is found at the lowest point of the curve in the diagram. This represents the point where the loop lies most deeply within the medulla.

Gaia refers to a controversial ecological hypothesis about how the Earth functions. Gondwanaland (or Gondwana) was a supercontinent formed by the breakup of Pangaea about 150 million years ago. It consisted of southern bodies of land including what are today South America, Australia, and Antarctica.

Tiny, air-filled sacs that terminate the airways within the lungs, the alveoli are where gas exchange happens in the lungs. The sacs are surrounded by a rich network of capillaries.

As the name might suggest, active transport requires energy from the cell. It uses this, for example, to power a protein carrier when sodium ions must be moved across a membrane and against a concentration gradient, as is done in the sodium-potassium pump.

Archaeopteryx existed about 150 million years ago during the late Jurassic, and showed a mix of birdlike (feathers on wings and tail) and reptilelike (teeth) characteristics.

At first, all dye molecules will move in one direction, from the first to the second side. As time passes, the dye particles will build in numbers on the second side, and some will begin to move back to side one. When this movement is equal in both directions, a point of dynamic balance (dynamic equilibrium or a steady-state) and constancy will be achieved.

Hemichordata, Urochordata, and Cephalochordata are all invertebrate subphyla in phylum Chordata.

In competitive inhibition, the competition is for the active site—will it be occupied by the substrate or the inhibitor? In noncompetitive inhibition, the inhibitor occupies an allosteric site and not the active site of the enzyme.

Vaso- refers to the vessels, and constriction or dilation describes whether they are getting smaller or larger. Broncho- refers to the lungs, specifically the bronchi or bronchioles.

Grasshoppers and butterflies are insects, spiders are arachnids, while clams and mussels are mollusks. Sea urchins and brittle stars are echinoderms (characterized by plates or spines in their body wall), as is the common sea star (starfish).

Cellular respiration is the process of freeing up the energy of organic compounds so it can be used by the cell. This process involves glycolysis, the Krebs cycle, and the electron transport system of the mitochondria.

Plankton, like other organisms at the lowest trophic level, will usually be present in the largest numbers (box A), and represented by the largest box. Herbivores are at the next trophic level and equal 11 (box B). Carnivores are at the top, and exist in the smallest number (1 in box C).

Human classification is as follows: Kingdom Animalia, Phylum Chordata, Class Mammalia, Order Primates, Family Hominidae, and finally Genus and species: Homo sapiens. Larger groups embrace the smaller. A phylum will usually consist of several to many classes, and each class may contain many orders.

All fibers within this unit are stimulated to contract simultaneously.

Choice A. may appear correct at first, but it is misleading. While an individual diploid organism can have only two alleles, a population of diploid organisms may contain many alleles.

The term transformation originated with the original work done by Griffith in the 1920s.

The glomerulus is a knot of capillaries surrounded by Bowmans capsule.

Cytokinesis is not part of mitosis proper. Some cells (such as muscle cells) may undergo nuclear division—mitosis—without subsequent cell division. An example is muscle cells, which are frequently multinucleate.

The DNA contains equal amounts of A (23%) and T (23%). The remaining amount of (100% - 46% = 54%) must contain equal amounts of C and G (27% of each).

Cocci (coccus) are spheres, bacilli (bacillus) are rod-shaped, and spirilla (spirillum) are twisted or coiled.

During anaerobic work, lactic acid is accumulated in muscles, and additional oxygen is required during recovery to metabolize this acid.

The morula (a solid ball of cells) precedes the formation of the blastula; gastrulation is the next phase of development.

As cell size increases, volume increases faster than surface area, yet all materials must enter or leave the cell through the surface. The diminishing amount of surface area per-unit-volume makes a large cell impossible.

A recessive allele is expressed in the homozygous state if the organism is homozygous-recessive. In the F1 offspring of a crossing of heterozygotes, one-quarter, on average, will show the recessive trait, as can be proved with a Punnett square.

Community is one step above population and one step below ecosystem in the hierarchy of the complexity of life. The ecosystem also includes the physical, non-living parts of the environment.

Plankton will usually be present in the largest numbers (box D), and therefore represented by the largest box, with herbivores at the next trophic level (shown in box E), followed by first-level carnivores (box F) and second-level carnivores (box G).

S stands for synthesis. During this stage of interphase, DNA is synthesized and chromosomes replicated.

Little or no parental care is typical of r-strategies. The point is to be quickly productive of a bulk of young, letting sheer numbers ensure the survival of some to reproduce. By contrast, K-strategists invest more, including parental care, in each of fewer young.

B-cells, which are part of the humoral immune system, differentiate into plasma cells to produce antibodies.

If a chemical reaction happens in an organism, it is safe to assume at least one enzyme was involved. This is true in cellular respiration and other metabolic activities of the cell. By lowering the energy of activation for reactions, enzymes make it easier for the reactions to occur.

Synapsis occurs early in meiosis I, and is the pairing of homologous chromosomes.

While much sulfur is stored in soils and sediments, sulfur in the form of sulfur dioxide and hydrogen sulfide are present as gases in the atmosphere. The major repositories for phosphorus are rock and deposits, from which phosphorus is released by the actions of water and weather.

The primary meristems (embryonic tissues) and their mature products are: (1) protoderm (makes epidermis); (2) procambium (produces primary vascular tissues); and (3) ground meristem (which makes ground tissue).

Adrenaline is a (mainly British) synonym for epinephrine. Acetylcholine is a neurotransmitter, and phenylephrine is a medication used as a decongestant. Insulin is produced in the pancreas, and aldosterone in the adrenal cortex.

These may also be called top carnivores

Watson and Crick proposed the DNA model, semi-conservative replication of DNA was proven by Meselson and Stahl, and the operon model is properly associated with Jacob and Monod. The one-gene, one-polypeptide hypothesis was suggested by Pauling and Itano.

Hydra are radially symmetrical, with their tentacles arranged around a common, central body axis. On superficial examination, turtles and crabs are round- or oval-shaped animals, but are nonetheless bilaterally symmetrical, as is the earthworm.

Roundworms (pinworms, hookworms) belong to phylum Nematoda. Flatworms (flukes, tapeworms) are members of phylum Platyhelminthes.

The collecting duct funnels the filtrate from the rest of the nephron toward the pelvis of the kidney, where it is conducted by the ureter to the urinary bladder.

Cytochromes are proteins that transfer electrons, and are found in chloroplasts, mitochondria, and endoplasmic reticulum.

Ginkos and cycads are often grouped with several other plants as gymnosperms.

If the non- is dropped, choice E. is a statement of the closely related Mendel's second law (law of independent assortment).

Cytokinins stimulate plant cell division

How and when DNA came to play its role is not yet understood.

In this instance, coevolution is a result of the selective pressures exerted by flowering plants and pollinators on each other. The other terms do not accurately express the unique relationship between these two groups of organisms.

It is the point at which the environment limits growth of a population. Of the remaining choices, choice D. comes closest to being a correct answer, but it fails, since carrying capacity is specific for each of the different populations in an environment. Choice C. is a basic description of the idea of biotic potential.

All the other primates listed, including humans, originated in the Old World. Platyrrhine monkeys are found in the New World. Their name refers to their broad, flat noses. New World monkeys are the only ones with prehensile tails.

One of the characteristic and telling features of the eukaryotic cell is the great amount of membrane found within the cell: characteristic, because no prokaryote possesses such a complex system of channels; telling, since it is a major clue to the organization of the eukaryotic cell. Eukaryotic cells are compartmentalized, and use membranes to sequester chemical activities, and as places to put activities such as those involving the transport of electrons.