Notes, abstracts, papers, exams and problems of Biology

Digesting Food

The Digestive Tract

The digestive tract is a long tube that extends from the mouth to the anus. Digestion begins in the mouth with chewing, breaking down food into smaller pieces for easier enzyme action.

Salivary glands secrete saliva containing enzymes like salivary amylase (begins carbohydrate digestion) and salivary lipase (begins fat digestion).

The Stomach

This mixture, called a bolus, is swallowed and travels down the esophagus to the stomach, passing through the lower esophageal sphincter. In the stomach, the bolus mixes with hydrochloric acid (HCl), pepsin (digests proteins), and gastric lipase (continues fat digestion). This creates a liquid called chyme, which exits the stomach through the pyloric sphincter to the duodenum... Continue reading "Digestive System: Process and Organs Explained" »

Biology Questions and Answers

Taxonomy and Evolution

1. Which of the following taxonomic categories contains all the others listed here? Class

2. Animals that possess homologous structures probably ___. evolved from the same ancestor

3. By definition, a clade is ___. monophyletic

Prokaryotes

4. What is the function of fimbriae? They are used to attach the cell to its substrate or to other prokaryotes.

5. Genes for the resistance of antibiotics are usually located _________. on plasmids

6. Which statement is true about obligate anaerobes? They are poisoned by O₂

7. The prokaryotic organisms most likely to be found living in salt ponds are the _____. halophiles

Ecology and Symbiosis

8. An ecological relationship between organisms of different species that

Meiosis is a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

Prophase I is divided into five stages: leptotene, zygotene, pachytene, diplotene, and diakinesis.

Phases of meiosis:

Prophase I: Chromosomes are formed from condensed chromatin.

Metaphase I: Bivalents are positioned on the equator of the cell.

Anaphase I: Homologous chromosomes are separated.

Telophase I: Chromosomes reach the spindle poles.

Prophase II: The meiotic spindle is re-created.

Metaphase II: the chromosomes, composed of two chromatids, align along the equator.

Anaphase II: The microtubules pull the chromatids to opposite poles of the cell. 

Telophase II: Four

Nerve Impulse Transmission Across a Synapse

The nerve impulse which has been transmitted along the membrane of the transmitter neuron reaches the end of its axon. At the end of the axon, the arrival of the nerve impulse causes neurotransmitters to be released into the synaptic cleft. Neurotransmitters bind to the membrane of the receptor neuron and generate a new nerve impulse. The new nerve impulse is transmitted along the membrane to the axon, where the whole process is repeated.

The Autonomic Peripheral Nervous System

The autonomic PNS consists of motor nerves which regulate the activity of the internal organs and control involuntary movements. The autonomic nervous system is divided into the sympathetic nervous system and the parasympathetic... Continue reading "Understanding Nerve Impulse Transmission and the Endocrine System" »

Human Reproduction

-Human reproduction is sexual and has two characteristics:

• The new individual is formed from a single cell, called a zygote.
• A zygote originates from the union (fertilisation) of two gametes or sex cells.

-Humans have two kinds of gametes: sperm and ova. Men produce sperm and women produce ova.

Puberty

Puberty begins in men with the first ejaculation (spermarche) and in women when the first menstruation takes place (menarche). Follicle stimulating hormone (FSH) and luteinizing hormone (LH). Puberty lasts around 3 to 4 years; Girls-> 10-13 years old, boys-> 12-14 years old.

Adolescence

During this stage many physical and psychological changes occur. These prepare the individual to develop their sexuality and makes them capable... Continue reading "Human Reproduction: Stages and Male Reproductive System" »

Trigeminal Nerve (V3) Anatomy

The trigeminal nerve (V3), also known as the mandibular nerve, has an anterior trunk (mainly motor) and a posterior trunk (sensory). It supplies taste sensory innervation to the anterior part of the dorsum of the tongue via fibers of CN7. Before dividing into two terminal trunks, there are two lateral branches:

• Meningeal branch: Sensory, supplies the dura mater of the middle cranial fossa.
• Medial pterygoid muscle nerve: Motor nerve, supplies the medial pterygoid muscle from the deep side. It also innervates the tensor veli palatini and tensor tympani muscles.

Anterior Trunk Branches

• Buccal nerve: Sensory, supplies the skin of the cheek, mucosa of the posterior and inferior portion of the vestibule, and the buccal side

Nervous System: The Body's Control Center

The Nervous System controls, processes, and responds to information, coordinating the body's activities.

Neuron: The Basic Unit of the Nervous System

The neuron is the basic structural unit of the nervous system. Neurons conduct impulses throughout the nervous system and consist of three regions:

• Axon
• Dendrites
• Cell Body

Dendrites and Axons: The Neuron's Extensions

Dendrites are extensions of the neuron that receive impulses and carry them toward the cell body.

The axon is an extension of the neuron that carries impulses away from the cell body toward other neurons, muscles, or glands.

Three Categories of Neurons

Neurons are categorized into three types:

1. Sensory Neurons: Carry impulses from the body to the spinal

MICROEVOLUTION

Changes that lead to the appearance of new species and groups that are closely related to each other.

MACROEVOLUTION

Leads to large groups of organisms after drastic change.

PUNCTUATED EQUILIBRIUM

The appearance of major groups of organisms took place as a result of drastic changes and the accumulation of gradual variations.

PHYSIOLOGICAL TREES

Visual representation of the evolutionary history of a group of organisms. A simplified diagram that, using a series of branches, shows the relationship between organisms.

SPECIATION

Two or more distinct species.

GEOGRAPHICAL BARRIERS

Examples are lakes, mountain ranges, and seas.

SEXUAL BARRIERS

Caused by anatomical changes that prevent mating from occurring.

PHYSIOLOGICAL BARRIERS

Incompatibilities... Continue reading "Evolutionary Processes and Theories: A Comprehensive Overview" »

Introduction

Humans are heterotrophs, meaning they cannot create their own organic matter. They obtain energy by ingesting substances from other organisms.

Food: Substances from other living things that are ingested.

Nutrients: Simple molecules contained in foods, necessary for life.

Eating: Conscious, voluntary process by which foods are taken from the outside environment.

Nutrition: Complex, unconscious, and mostly involuntary process by which foods are transformed into nutrients.

Carbohydrates (Glucides)

Energy-providing nutrients.

Monosaccharides

Formed only by one molecule.

• Examples: Glucose (cane sugar), fructose (fruit sugar)

Disaccharides

Formed by two molecules.

• Examples: Sucrose (cane sugar), lactose (sugar of milk)

Mono and disaccharides are sweets,... Continue reading "Nutrients: Essential Substances for Life" »