After food has been masticated in the oral cavity, where does it go next?

Skeletal muscle: This muscle cell is striated, long, and cylindrical. There are many nuclei in a skeletal muscle cell. Attached to bones in the body, skeletal muscle contracts voluntarily, meaning that it is under conscious control.

Smooth muscle: This muscle consists of nonstriated muscle cells that are spindle-shaped. Like cardiac muscle cells, smooth muscle cells contain one nucleus. This muscle type is found in the walls of internal organs like the bladder and stomach. Smooth muscle contraction is involuntary and controlled by the autonomic nervous system.

Cardiac muscle: This muscle consists of muscle cells that are striated, short, and branched. These cells contain one nucleus, are branched, and are rectangular. Cardiac muscle contraction is an involuntary process, which is why it is under the control of the autonomic nervous system. This muscle is found in the walls of the heart.

Taxonomy is the process of classifying, describing, and naming organisms. There are seven levels in the Linnaean taxonomic system, starting with the broadest level, kingdom, and ending with the species level. For example, in the image the genus level contains two types of bears, but the species level shows one type. Additionally,organisms in each level are found in the level above it. For example, organisms in the order level are part of the class level. This classification system is based on physical similarities across living things. It does not account for molecular or genetic similarities.

One step of the scientific method is to analyze information or data collected from the experiment to conclude whether the hypothesis is supported.

Recall that these make up thescientific method,described below:

• Problem:The question created because of an observation.Example: Does the size of a plastic object affect how fast it naturally degrades in a lake?
• Research:Reliable information available about what is observed.Example: Learn how plastics are made and understand the properties of a lake.
• Hypothesis:A predicted solution to the question or problem.Example: If the plastic material is small, then it will degrade faster than a large particle.
• Experiment:A series of tests used to evaluate the hypothesis. Experiments consist of anindependent variablethat the researcher modifies and adependent variablethat changes due to the independent variable. They also include acontrol groupused as a standard to make comparisons.
  • Example: Collect plastic particles both onshore and offshore of the lake over time. Determine the size of the particles and describe the lake conditions during this time period.
• Observe:Analyze data collected during an experiment to observe patterns.
  • Example: Analyze the differences between the numbers of particles collected in terms of size.
• Conclusion:State whether the hypothesis is rejected or accepted and summarize all results.
• Communicate:Report findings so others can replicate and verify the results.

Before mitosis or meiosis occurs, interphase must happen. This is when the cell cycle takes place. The cell cycle is an organized process divided into two phases:interphaseand theM (mitotic) phase. During interphase, the cell grows and copies its DNA. After the cell reaches the M phase, division of the two new cells can occur. The G1, S, and G2phases make up interphase.

Human intercourse consists of the male introducing sperm into the female’s reproductive system. Sperm may then pass through the female’s reproductive system to the Fallopian tubes where one sperm fertilizes an ovum, creating azygote. The zygote passes out of the Fallopian tube and implants into the uterine wall to begin gestation. Over nine months, the zygote develops and grows into an embryo and then a fetus. An infant is the baby that is born.

There are two major types of receptor molecules that respond to an intercellular chemical signal:

• Intracellular receptors: These receptors are located in either the cytoplasm or the nucleus of the cell. Signals diffuse across the cell membrane and bind to the receptor sites on intracellular receptors, of the same cell.
• Membrane-bound receptors: These receptors extend across the cell membrane, with their receptor sites on the outer surface of the cell membrane. They respond to intercellular chemical signals that are large, water-soluble molecules that do not diffuse across the cell membrane.

A control group is a factor that does not change during an experiment. Due to this, it is used as a standard for comparison with variables that do change such as a dependent variable.

Recall that these make up thescientific method,described below:

• Problem:The question created because of an observation.Example: Does the size of a plastic object affect how fast it naturally degrades in a lake?
• Research:Reliable information available about what is observed.Example: Learn how plastics are made and understand the properties of a lake.
• Hypothesis:A predicted solution to the question or problem.Example: If the plastic material is small, then it will degrade faster than a large particle.
• Experiment:A series of tests used to evaluate the hypothesis. Experiments consist of anindependent variablethat the researcher modifies and adependent variablethat changes due to the independent variable. They also include acontrol groupused as a standard to make comparisons.
  • Example: Collect plastic particles both onshore and offshore of the lake over time. Determine the size of the particles and describe the lake conditions during this time period.
• Observe:Analyze data collected during an experiment to observe patterns.
  • Example: Analyze the differences between the numbers of particles collected in terms of size.
• Conclusion:State whether the hypothesis is rejected or accepted and summarize all results.
• Communicate:Report findings so others can replicate and verify the results.

Mendel developed theories of genetics that scientists around the world use today.

From experiments with garden peas, Mendel developed a simple set of rules that accurately predicted patterns of heredity. He discovered that plants eitherself-pollinateorcross-pollinate, when the pollen from one plant fertilizes the pistil of another plant. He also discovered that traits are eitherdominantorrecessive. Dominant traits are expressed, and recessive traits are hidden.

Mendel’s Theory of Heredity

To explain his results, Mendel proposed a theory that has become the foundation of the science of genetics. The theory has five elements:

• Parents do not transmit traits directly to their offspring. Rather, they pass on units of information calledgenes.
• For each trait, an individual has two factors: one from each parent. If the two factors have the same information, the individual ishomozygousfor that trait. If the two factors are different, the individual isheterozygousfor that trait. Each copy of a factor, orgene, is called anallele.
• The alleles determine the physical appearance, orphenotype. The set of alleles an individual has is itsgenotype.
• An individual receives one allele from each parent.
• The presence of an allele does not guarantee that the trait will be expressed.

Blood continually flows in one direction, beginning in the heart and proceeding to the arteries, arterioles, and capillaries. When blood reaches the capillaries, exchanges occur between blood and tissues. After this exchange happens, blood is collected into venules, which feed into veins and eventually flow back to the heart’s atrium. The heart must relax between two heartbeats for blood circulation to begin.

Two types of circulatory processes occur in the body:

Systemic circulation

• The pulmonary vein pushes oxygenated blood into the left atrium.
• As the atrium relaxes, oxygenated blood drains into the left ventricle through the mitral valve. 3. The left ventricle pumps oxygenated blood to the aorta.
• Blood travels through the arteries and arterioles before reaching the capillaries that surround the tissues.

Pulmonary circulation

• Two major veins, the Superior Vena Cava and the Inferior Vena Cava, brings deoxygenated blood from the upper and lower half of the body.
• Deoxygenated blood is pooled into the right atrium and then sent into the right ventricle through the tricuspid valve, which prevents blood from flowing backward.
• The right ventricle contracts, causing the blood to be pushed through the pulmonary valve into the pulmonary artery.
• Deoxygenated blood becomes oxygenated in the lungs.
• Oxygenated blood returns from the lungs to the left atrium through the pulmonary veins.

A pH of 7 is a neutral solution, which is how pure water is classified. Researchers can determine the strength of an acid or a base by measuring the pH of a solution. The pH value describes how acidic or basic a solution is. On pH scale, shown below, if the number is less than 7 the solution is acidic. A pH greater than 7 means the solution is basic. When the pH is exactly 7, the solution is neutral.