Notes, abstracts, papers, exams and problems of Biology

Gas Exchange

Blood is circulated to the lungs to obtain oxygen. This happens in the alveoli. Air entering the lungs has a higher concentration of oxygen and a lower concentration of carbon dioxide than the air that the lungs release. The blood exiting the lungs has a higher oxygen concentration and a lower carbon dioxide concentration than when it enters. The amount of nitrogen remains constant. Oxygen passes through the alveolar wall. These gases traverse the membrane of the cells by diffusion.

What Happens Inside the Alveoli?

The total surface area of the lungs' alveoli is enormous. Each alveolus is surrounded by many tiny blood vessels called capillaries, and the wall is extremely thin.

Microorganisms in the Air

Upper respiratory illnesses like... Continue reading "Human Biology: Respiration, Microorganisms, and Nutrition" »

The Endocrine System

The endocrine is made up of coordinated groups of glands called endocrine glands. They are called endocrine because they release hormones into the bloodstream.

Hormones

Hormones are chemical messengers that activate or stop, accelerate or delay many processes carried out by organs and tissues.

Health Diet (E.S)

Healthy diet, regulate moderate-intensity exercise, and don't consume drugs.

Health Diet

Healthy diet, exercise regularly, and practice correct postures.

The Control of Hormone Secretion

Feedback mechanisms in the endocrine system act similarly. When the amount of hormone in the blood reaches a specific level, a signal makes the gland stop releasing it.

How Hormones Work:

1. Stimulated endocrine glands respond by producing hormones

Stages of Cell Division

Prophase: The first stage of cell division, before metaphase, during which the chromosomes become visible as paired chromatids and the nuclear envelope disappears. The first prophase of meiosis includes the reduction division.

Metaphase: The second stage of cell division, between prophase and anaphase, during which the chromosomes become attached to the spindle fibers.

Anaphase: The stage of meiotic or mitotic cell division in which the chromosomes move away from one another to opposite poles of the spindle.

Telophase: The final phase of cell division, between anaphase and interphase, in which the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed.

Cytokinesis: The cytoplasmic division of... Continue reading "Cell Division, Reproduction, and Biological Processes" »

Genetics Terminology

Basic Concepts

• Trait: An inheritable characteristic of an organism.
• Gene: A DNA segment containing information that controls a specific trait.
• Allele: A variant form of a gene, often arising from mutations, contributing to hereditary variations.
• Locus (pl. Loci): The specific location of a gene on a chromosome.

Zygosity

• Homozygous Organism: Possesses identical alleles for a given gene (e.g., AA or aa).
• Heterozygous Organism: Possesses different alleles for a given gene (e.g., Aa).

Allele Interactions

• Dominant Allele: An allele that expresses its phenotype regardless of the paired allele.
• Recessive Allele: An allele that expresses its phenotype only when paired with an identical allele.

Genetic Inheritance Patterns

• Dominance (Dominant

Genome

Autotrophs and Heterotrophs Defined

F.5.1 Define the terms photoautotroph, photoheterotroph, chemoautotroph, and chemoheterotroph

Photoautotroph: An organism that uses light energy to generate ATP and produce organic compounds from inorganic substances.

Photoheterotroph: An organism that uses light energy to generate ATP and obtains organic compounds from other organisms.

Chemoautotroph: An organism that uses energy from chemical reactions to generate ATP and produce organic compounds from inorganic substances.

Chemoheterotroph: An organism that uses energy from chemical reactions to generate ATP and obtains organic compounds from other organisms.

Examples of Autotrophs and Heterotrophs

F.5.2 State one example of a photoautotroph, photoheterotroph,

Animal Respiration

Breathing is essential for respiration. Animals breathe by inhaling oxygen and exhaling carbon dioxide. This gas exchange occurs via the respiratory system.

Respiratory Systems

Respiratory systems require thin, moist surfaces covered in blood vessels for efficient gas exchange. This facilitates oxygen uptake and carbon dioxide expulsion.

Cutaneous Respiration

Gas exchange through the skin (thin and moist). Examples include earthworms and adult amphibians.

Branchial Respiration

Gas exchange through gills (surrounded by blood vessels). Examples include fish and some crustaceans.

Tracheal Respiration

Gas exchange via internal tubes (tracheae) carrying air directly to cells. Examples include terrestrial arthropods.

Pulmonary Respiration

Gas... Continue reading "Animal Respiration, Circulation, and Excretion" »

Evidence of Evolution

1. Anatomical and Morphological Evidence:

• Homologous organs
• Analogous and vestigial organs

Fossils reveal that organisms in the Earth's past were different from nowadays.

Some embryos from different species are similar, indicating an evolutionary relationship between them.

Biogeographical patterns can be explained according to theories of evolution.

Molecular similarities reveal the degree of relatedness between two groups.

• Parasites: organisms that live off other species.
• Behavior: based on genetic inheritance.

Present-Day Theories of Evolution

Neo-Darwinism considers that natural selection does not act on the individual in isolation... Continue reading "Evidence of Evolution and Present-Day Theories" »

The Senses of Hearing

5) THE SENSES OF HEARING:

6) THE HEALTH OF THE SENSE ORGAN:

Short-sightedness (myopia): distant objects appear out of focus because the eyeball is too long, so images are focused in front of the retina. Concave lenses or surgery can correct the problem.

Long-sightedness (hypermetropia): close objects appear out of focus because the eyeball is too short. This causes images to be focused behind the retina. Convex lenses or surgery can correct the problem.

Astigmatism: objects appear distorted or blurred. It is caused by an irregularly shaped cornea. Lens or surgery can correct the problem.

Cataracts: the crystalline lens loses its transparency until it becomes opaque. This causes progressive loss of vision and possible blindness.... Continue reading "The Senses of Hearing and Health of Sense Organs" »

These are energetic and structural substances found in many foods that we eat daily. There are two groups:

Simple Carbohydrates

• Monosaccharides: They are the simplest ones.
• Disaccharides: They are formed by two monosaccharides joined together.

Complex Carbohydrates (Polysaccharides)

They are neither sweet nor crystalline and they are not soluble in water. They include:

• Starch: It is made up of glucose molecules.
• Cellulose: It makes up vegetal fibre and forms the plant cellular wall. It is also made up of glucose molecules.

Inorganic Substances

These are small inorganic substances with variable composition. In solid state, they are structural. In dissolution, they are regulatory and allow our organs to function correctly and intervene in the regulation.... Continue reading "Energetic and Structural Substances in Foods" »