Notes, summaries, assignments, exams, and problems for Biology

Arthropoda

Hard skeleton made of chitin and protein.

Possess numerous jointed appendages and a segmented body.

They can fly fast; they must molt to grow.

Porifera

Most of them are marine while a few are freshwater forms.

These are multicellular organisms which are sedentary in nature.

Body is cylindrical, asymmetrical, or has radial symmetry.

Most of them are marine while a few are freshwater forms.

Cnidaria

Two tissue layers with nerve and muscle tissue.

A mouth and stomach.

Nematocysts: harpoon-like structures contained in special cells called cnidocytes.

Two main life forms: free-swimming medusa and attached polyp.

Basic anatomy of cnidarians

They are similar to sponges. Cnidarians are diploblasts, meaning that they develop from two basic germ cell layers:... Continue reading "Invertebrate Phyla: Arthropoda, Porifera, Cnidaria, Mollusca, Echinodermata" »

DNA Deoxyribonucleic Acid Forming Chromosomes

Stores genetic info DNA wounded to histones which becomes nucleosome loops onto chromatin

Codes for protein twisted into chromatid looped and packed into chromosome

Nucleotide Chromatin fibers are coiled and condensed to form chromosomes

consisting of a nitrogen-containing base Histones are proteins that help package and organize DNA in the nucleus of

(a, g, t, c.) or uracil in RNA eukaryotic cells by forming nucleosomes around which DNA is wrapped.

- phosphate group nucleosome is a basic unit of DNA packaging in eukaryotic cells

- sugar chromatid is one of the two identical copies of a replicated chromosome

Homologous Chromosomes chromosome is a long, coiled-up strand of DNA that contains genetic information

chromosomes... Continue reading "Understanding DNA, Chromosomes, and Genetic Variation" »

The Spinal Bulb

The spinal bulb (medulla oblongata) is an extension of the spinal cord. It consists of grey matter surrounded by white matter. There are neural pathways that carry information, and these pathways cross; thus, the right side of the brain receives information from the left side of the body, and the left side of the brain receives information from the right side of the body.

Functions of the Spinal Bulb and Hypothalamus

It performs different functions, including:

• Regulating the process of sleep.
• Regulating visual and auditory reflexes.
• Regulating blood pressure.
• Coordinating communication between the cerebrum and other parts of the brain.

It contains an important part called the hypothalamus, which controls the pituitary gland, which in... Continue reading "Human Nervous System Structure and Functions Explained" »

Understanding Pathogens: Viruses and Bacteria

Infectious diseases are caused by various pathogens, primarily viruses and bacteria, affecting different systems of the human body. Below is a summary of common diseases, their classification, and typical symptoms.

Common Viral Infections

• Influenza (Flu)

  System Affected: Respiratory System

  Classification: Virus

  Symptoms: Fever, body aches, tiredness, and cough.

• Herpes Simplex Virus (HSV)

  Classification: Virus (DNA)

  After the initial infection, the virus remains inactive in the human body and later reactivates under certain circumstances, such as stress, menstruation, or temperature changes. Symptoms are highly variable, and herpes lesions can appear anywhere on the body.

• Human Immunodeficiency Virus (HIV)

Carbohydrates

• Monosaccharides: Glucose, ribose, fructose.
• Disaccharides: Maltose (two glucose molecules), sucrose (glucose and fructose).
• Polysaccharides: Cellulose and glycogen (chains of glucose).

Fatty Acids

• Cis-unsaturated fatty acids: Bended structure, loosely packed, low melting point, hydrogen atoms on the same side, liquid at room temperature, common in nature.
• Trans-unsaturated fatty acids: Straight structure, strongly packed, high melting point, hydrogen atoms on opposite sides, solid at room temperature, rare in nature.

Amino Acids and Proteins

Amino acids consist of an amino group (-NH2) and a carboxyl group (-COOH).

Common Amino Acids

Serine, glutamic acid, alanine, and glycine.

Amino Acid Structure

Amino acids linked together share identical... Continue reading "Biological Macromolecules: Carbohydrates, Lipids, and Proteins" »

Sexual Reproduction & Meiosis

Sexual Reproduction: Takes place when two sex cells, or gametes, from two parents of different sexes join together.

Meiosis: A cell division process through which haploid cells are formed.

Fundamental Genetic Concepts

• Traits: Each of the characteristics present in an organism that can be inherited by its offspring.
• Gene: A section of DNA that contains information about a certain trait and controls that trait.
• Alleles: Different forms of a gene.
• Homozygous: When two alleles for a specific trait are identical (e.g., AA, aa).
• Heterozygous: When two alleles for a specific trait are different (e.g., Aa).
• Genotype: An organism's complete set of genes.
• Phenotype: The observable way in which a genotype is expressed under specific

Trophic Levels

A trophic level consists of all organisms within an ecosystem that share the same feeding strategy.

Producers

Producers are autotrophic organisms that perform photosynthesis, using solar energy to convert inorganic matter into organic matter.

Consumers

Consumers are heterotrophic organisms that obtain energy by consuming other living organisms.

Primary Consumers

Primary consumers are herbivores that feed directly on producers.

Secondary Consumers

Secondary consumers are carnivores that feed on primary consumers.

Tertiary Consumers

Tertiary consumers (supercarnivores) are carnivores that feed on secondary consumers, such as lions.

Decomposers

Decomposers are heterotrophic organisms that break down dead organisms and waste products, returning... Continue reading "Ecosystem Dynamics: Trophic Levels, Food Chains, and Energy Flow" »

Cardiovascular System: Key Definitions

Cardiovascular Disease

It can be caused by smoking, poor diet, stress, physical inactivity, or hereditary factors.

Atherosclerosis

It is the hardening of artery walls caused by the buildup of cholesterol and lipids.

Hypertension

It is abnormally high blood pressure.

Heart Attack

It occurs when an artery that supplies blood to the heart becomes blocked.

Stroke

It occurs when a blood vessel in the brain becomes blocked or bursts.

Respiratory System Anatomy

The main parts of the respiratory system include:

• Nasal Cavities
• Mouth
• Pharynx
• Larynx
• Trachea (Windpipe)
• Bronchus
• Bronchiole
• Alveoli
• Lungs
• Diaphragm

Respiratory System Part Identification

1. It is the organ that produces the sense of smell: Nose/Nasal Cavity
2. It is also known as the

Explain the process of nutrient absorption

The pancreas, liver, and gallbladder assist with digestion in the small intestine. The large intestine removes water and converts food waste into feces.

Digestive system functions

• Tongue: Pushes food down the pharynx.
• Salivary glands: Produce saliva which helps break down food particles.
• Pancreas: Produces enzymes that aid digestion.
• Liver: Produces bile.
• Gallbladder: Stores bile.

Waste removal processes

1. Production of sweat.
2. Exhalation of carbon dioxide.
3. Production of urine and feces.

Excretory system labels and functions

• Kidneys: Remove waste from the bloodstream.
• Ureter: Connects the kidneys to the bladder.
• Bladder: Stores urine.
• Urethra: Exits urine from the body.

Brain anatomy and functions

• Cerebrum: Controls movements

1. Essential Atmospheric Layers

The troposphere and the stratosphere are the most important layers for life. The atmospheric structure includes:

• Troposphere: The lowest layer (contains the tropopause and ozone maximum).
• Stratosphere: Located above the troposphere.
• Mesosphere: Includes the mesopause.
• Thermosphere: The highest layer.

2. Primary Atmospheric Gases

The atmosphere is composed mainly of Nitrogen (78.9%) and Oxygen (20.95%). Other trace gases include:

• Argon: 0.93%
• CO2: 0.038%
• Traces of neon, helium, methane, water vapor, krypton, hydrogen, xenon, and ozone.

3. Climate Influencing Factors

The two abiotic factors that influence climate the most are temperature and moisture.

4. Solar Radiation Distribution

Solar radiation reaching Earth is either reflected... Continue reading "Earth's Atmosphere and Ozone Layer Facts" »