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

The Biosphere

The biosphere is the set of all living things on Earth.

Understanding Ecosystems

An ecosystem consists of interconnected components:

• Biotic Components: Living things that inhabit a particular place and interrelate.
• Abiotic Components: All the physical environmental conditions or non-living elements within the dwelling of living beings.

Relations Between Components: Living organisms in a specific location are adapted to certain conditions of their physical environment and, in turn, modify it.

Ecological Relationships

There are relationships between individuals of the same species and between different species, such as predation, parasitism, symbiosis, and commensalism.

Photosynthesis

Photosynthesis is the process of converting light energy... Continue reading "Understanding Earth's Living Systems" »

Kinds of Amino Acids

Amino acids can be classified into several categories:

• Nonpolar:
  • Aliphatic
  • Aromatic
• Polar Uncharged
• Charged:
  • Acidic (Anionic)
  • Basic (Cationic)

Proteins: Building Blocks of Life

Proteins are biopolymers formed by molecular chains of 20 different amino acids, each with its own characteristics.

Protein Structures

Primary Structure

The primary structure is characterized by the specific composition of amino acids and their sequential order within the polypeptide chain.

Secondary Structure

The secondary structure refers to the folding of the primary structure due to the formation of hydrogen bonds between the -C=O group of one peptide bond and the -NH group of another. This results in the side chains (R groups) adopting specific spatial arrangements... Continue reading "Amino Acids and Protein Structures: A Comprehensive Look" »

Ecosystems: Definition and Characteristics

An ecosystem is a system formed by the interaction between a community and a biocenosis, or physical environmental factors. An ecosystem model for the subject is closed but open to energy, being capable of regulating itself and remaining in dynamic equilibrium over time.

Population Dynamics

A population is comprised of a set of individuals of the same species living in a particular location. There are some factors that prevent a population from reaching its full biotic potential. These can be external or internal to the population:

• External Factors: These may be biotic (predators, parasites, or diseases caused by other agencies competing for a given resource) and abiotic (climate change, food shortages,

• In the pyramids of numbers, the lengths of the steps are proportional to the number of individuals of all species in each trophic level per unit area or volume.

  Biomass in the lengths of the steps are proportional to the dry weight of all individuals in each trophic level per unit area or volume.

  These pyramids best describe the trophic relationships of the ecosystem as they indicate the amount of organic matter that can be eaten at each trophic level, but do not express the amount transferred from one level to another.

  Energy in the lengths of the steps are proportional to the energy produced per unit time of all individuals in each trophic level per unit volume or surface.

  These pyramids provide a better overall picture of trophic relationships

Cholera

Pathogen: Vibrio cholerae

Methods of Transmission:

• Foodborne
• Waterborne

Note: 3/4 of infected people may be asymptomatic carriers and pass large numbers of bacteria in their feces.

Global Distribution: Asia, Africa

Incubation Period: 1-5 days

Site of Action: Wall of the small intestine; secretes a toxin called choleragen

Clinical Features:

• Severe diarrhea
• Loss of water and salts
• Weakness

Note: Can be fatal if not treated within 24 hours.

Method of Diagnosis: Microscopic analysis of feces

Annual Incidence Worldwide: 5.5 million

Annual Mortality Worldwide: 120,000

Treatment: Antibiotics

Tuberculosis

Pathogen: Mycobacterium tuberculosis

Transmission:

• Airborne droplets
• Infected meat

Global Distribution: Worldwide

Incubation Period: A few weeks or months

Site of

Infection: Pathogen Penetration and Host Response

Infection is the penetration of a pathogen into the body of an animal or plant, causing changes in organs and their functions. It is essential for the microbe to possess pathogenicity (the ability to cause disturbances in the body), which depends on its invasiveness and toxin production. For an infection to develop, the host organism must be receptive to the microbes (i.e., susceptible to invasion).

Organic Defense Mechanisms: Protecting the Body

Nonspecific Defense (External Barriers)

These are the body's first lines of defense, acting as external barriers:

• Structural: Skin and mucous membranes. These are common entry points for pathogens when compromised.
• Mechanical: Tears, urine, coughing, and

Divisions of the Nervous System

Central Nervous System

Consists of the brain and spinal cord. It is responsible for receiving and processing information to control bodily functions.

Peripheral Nervous System

Consists of a set of nerves that connect the central nervous system with other organs of the body.

Components of the Central Nervous System

The brain is housed in the skull. The main parts are the cerebrum, the cerebellum, and the medulla oblongata.

The Cerebrum

Appears divided into two hemispheres. The outer part consists of gray matter that receives information from sense organs. The inner zone contains white matter.

The Cerebellum

Located below the cerebrum. The cerebellum coordinates movements such as walking and allows us to maintain balance.... Continue reading "Nervous System: Structure, Function, and Health" »

Infectious Disease Prevention and Treatment

Infections can be treated with antiseptics, which kill microorganisms but can only be applied to the skin's surface. Antibiotics are substances that selectively attack bacteria and can be ingested or injected. Penicillin was the first known antibiotic. The English physician Jenner invented vaccines, which involve injecting small amounts of dead or fragmented pathogens.

Healthy Habits

• Eat in moderation at least three times a day, always including breakfast.
• Eat a balanced diet with the appropriate proportion of nutrients.
• Sleep eight hours a day.
• Exercise moderately to maintain muscle tone.
• Maintain a proper weight for your age, sex, and build.
• Practice proper hygiene.
• Avoid snuff, alcohol, and other drugs.

Evolutionism

According to biology, fixism maintained that the existing living species were independent and immutable and that they had always existed with the same basic characteristics.

From the works of Lamarck and Darwin, evolutionism emerged. It holds that the universe and life in all its manifestations, and therefore all species, are the result of change and adaptation. This theory is called evolution and argues that species living today come from others who have disappeared, and these in turn from another, until reaching the first living organisms. For evolution, all living creatures belong to a single large family that has developed over Earth's history.

Early Evolutionary Theories

Scientists disagree on:

• The mechanisms causing species diversification.