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

Components and Dynamics of Ecosystems

Defining Ecosystem Components

• Biotope: Encompasses the non-living components of the ecosystem, such as rocks and water, or physical conditions like temperature.
• Biocoenosis: Is made up of all the living organisms that inhabit the biotope.

Interactions in the Ecosystem

• Abiotic Factors: Affect the biocoenosis (e.g., soil and low temperatures).
• Biotic Factors: Affect the biotope (e.g., herbaceous plants increasing the number of herbivores).

Adaptations to the Environment

Adaptation is an adjustment in the body or behavior of an organism to its environment.

1. Anatomical Adaptations: Physical characteristics of living things that enable them to carry out a specific activity.
2. Behavioral Adaptations: Actions that organisms

Digestive System Organs

Esophagus

• Tube approximately 25 cm long.
• Located behind the trachea and in front of the spinal cord.
• Drives the food bolus from the pharynx to the stomach.
• Its muscles produce peristaltic movements to ensure food reaches the stomach.
• Produces mucus, which favors food transit.

Pylorus

• A sphincter that communicates with the small intestine (duodenum).

Shared & Digestive System Components

Pharynx

• A duct located behind the mouth.
• Contains lumps called tonsils.
• Communicates the mouth with:
  • Esophagus
  • Back of the nostrils
  • Larynx
  • Middle ear

Epiglottis

• A flap located in the lower part of the pharynx.
• Closes the entrance to the larynx during swallowing.
• Prevents food from entering the respiratory tract.

Cardia (Cardiac Sphincter)

• A sphincter that

vitamin a : fish liver oils, animal liver. Function: required for normal immune system function and for production of cells in retina of eye. 

Microorganisms: Bacteria and Viruses

Bacteria: Key Characteristics

Bacteria are single-celled, prokaryotic microorganisms. They possess ribosomes, typically around 1000nm in size.

Viruses: Key Characteristics

Viruses are non-cellular genetic elements that are obligate intracellular parasites, meaning they must use living cells to reproduce. Their size ranges from approximately 20-300nm.

Viral Structure Explained

A typical viral structure includes:

• Nucleic Acid (Genome): This is the genetic material, which can be either DNA or RNA.
• Capsomeres: Protein subunits that assemble to form the capsid.
• Viral Nucleocapsid: The combined structure of the nucleic acid and its surrounding protein capsid.
• Core Wall (Capsid/Envelope): A protective shell, often referred

• Ecology is the scientific study of the interactions between organisms and the living and nonliving components of their environment.
• Organismal ecology studies how an organism’s structure, physiology, and (for animals) behavior meet environmental challenges.
• A population is a group of individuals of the same species living in an area.
• Population ecology focuses on factors affecting population size over time.
• A community is a group of populations of different species in an area.
• Community ecology examines the effect of interspecific interactions on community structure and organization.
• An ecosystem is the community of organisms in an area and the physical factors with which they interact.
• Ecosystem ecology emphasizes energy flow and chemical cycling

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" »

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)

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