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

Invertebrate Excretory Systems (Protonephridia): These are found in animals with no coelom, such as flatworms. They consist of highly branched tubes that end in a few cells with cilia (flame cells) or flagella (solenocytes). Both cilia and flagella are located in the lumen of the tube, and their movement causes the continuous elimination of waste substances. (Metanephridia): This system occurs in coelomates (annelids, mollusks, etc.). It is made up of a coiled tube surrounded by a capillary network, with two openings: the external (nephridiopore) and internal (nephrostome), which opens into the coelomic cavity. Inside the metanephridia, reabsorption occurs for compounds that are still useful, while waste substances are expelled outside through... Continue reading "Understanding Invertebrate and Vertebrate Excretory Systems" »

Connective Tissue Functions and Components

Connective tissues provide a frame to attach the other tissues of the body, such as body structures, and to protect the internal organs. The intercellular substance of these tissues is very important and is reinforced by a matrix of fibers dispersed and interwoven, and a transparent amorphous extracellular matrix.

Specialized Cell Types

• Fibroblasts: Fixed cells, which are variable.
• Adipocytes; Monocytes: Accumulate fat; WBC migrants. When inflammation occurs, they turn into macrophages that engulf microbes.
• Lymphocytes: Produce antibodies.
• Mast cells: They produce heparin (anticoagulant function) and histamine, which increases the permeability of capillary walls.
• Chromatophores: Stem cells that are very bulky.

Neodarwinism

This theory, born in 1947, defines evolution based on six core principles:

1. Refusal of Lamarckism

   It does not accept the theory of acquired characteristics.

2. Variability: Mutation and Recombination

   Individuals with asexual reproduction have mutation as the only source of variability. Individuals in sexual reproduction involve the process of genetic recombination.

3. Natural Selection Acts on Genetic Variability

   The individual is the bearer of different alleles, and natural selection acts on these varieties.

4. Evolution Occurs in the Population, Not Individuals

   A population is defined as a group of individuals of the same species that share an area and can crossbreed to produce fertile offspring. Populations survive, change, and evolve, while individuals

Hominid Cranial Evolution and Physical Traits

The Australopithecus possessed a larger cranium than its predecessors, featuring an accentuated undershot jaw and a marked supraorbital rim; its teeth were human-like. Homo ergaster adapted to hard foods and maintained a large habilis-like cranium with a developed supraorbital arch and small teeth. Homo erectus consumed softer foods, utilized fire, and featured a low oblique border with a prominent face. Homo antecessor displayed a solid jaw and a combination of modern and archaic characters.

Neanderthals, associated with cannibalistic practices, had a highly developed musculature, standing approximately 1.65m tall, and a long cranium. The modern hominid features a brain-based bipedal structure with... Continue reading "Human Evolution and Biological Theories of Adaptation" »

Unit 10: The Basis of Heredity - Molecular Genetics

Basics of Genetics

• Gene: Each piece of DNA containing information for one character.
• Alleles: Each form a gene can have.
• Locus: The physical location a gene occupies on a chromosome.
• Loci: The place occupied by several genes.
• Diploid Organisms: Individuals who have two alleles for each gene, one from the mother and one from the father. This is represented as 2n.
• Haploid Organisms: Individuals that have only one gene for each character. This is represented by n.
• Gamete: A sexual reproductive cell, haploid (n), produced by meiosis.
• Genotype: The set of alleles of an individual for one or more characters.
• Phenotype: Each of the aspects or observable manifestations of a character.
• Phenotype = Genotype +

Lipids

Functions of Lipids

• Energy Storage: Lipids serve as the primary energy reserve in the body.
• Structural Components: Lipid bilayers form the plasma membrane and other cell organelles.
• Protection: Lipids cushion vital organs, like the kidneys, and protect body surfaces (e.g., waxes on hair and fruit).
• Biocatalysis: While not all lipids are biocatalysts themselves, some play a role in biocatalyst synthesis.
• Transport: Lipids are emulsified and transported from the intestine to either storage in adipose tissue or sites of utilization.

Amino Acids

Amino acids are small organic compounds characterized by a carboxyl group and an amino group. They are solid, crystalline, water-soluble, have high melting points, and exhibit optical activity. Primary amino... Continue reading "Lipids, Amino Acids, and Proteins: Structure, Function, and Properties" »

1. Health and Disease

When all organs and body systems function correctly, we consider ourselves healthy. If any part of the body is impaired and cannot perform its function properly, it causes disease. When a person becomes ill, characteristic symptoms of the disease appear, often accompanied by some deterioration. Key factors in maintaining health include:

• A proactive approach to health.
• Adopting healthy habits and lifestyles.
• Personal characteristics such as age or hereditary factors.
• An effective health system.

2. Disease Categories

Diseases can be categorized in various ways:

• Infectious: Caused by microorganisms that enter the body and can be transmitted from person to person.
• Non-infectious: Not caused by microorganisms and therefore not transmitted

Tissues: Types, Structure and Function

Tissue: a group of cells that assemble and function together. Between cells is the intercellular substance (extracellular matrix). Cells can be closely packed together or separated by this intercellular material.

Epithelial Tissue

Epithelial (covering) tissues form protective layers such as skin (the outer layer). They also form mucous membranes that line internal cavities and surfaces, and they include secretory tissues (glands). Epithelial tissues are made of crowded cells with little intercellular substance and may be arranged in one or several layers.

Nervous Tissue

Nervous tissue consists of neurons and supporting cells. It transmits nerve impulses and is responsible for coordination, sensation, and the... Continue reading "Tissues, Cells, Organs & Biomolecules: Structure and Function" »

The Chemical Foundations of Life

The components that constitute the majority of life are oxygen, hydrogen, and carbon, which comprise 98% of our body. Water acts as an essential solvent. Living organisms obtain energy through chemical reactions involving organic matter, primarily produced via photosynthesis by plants, algae, and some bacteria.

Energy Production and Metabolism

For organic matter synthesized in photosynthesis to produce the energy necessary for life, a process called cellular respiration is required. Depending on how organisms obtain organic matter, they are classified as:

• Autotrophs: Produce their own food.
• Heterotrophs: Consume other organisms for energy.

The Origins of Life on Earth

Life requires various mechanisms to adapt to changing... Continue reading "The Origins and Evolution of Life on Earth" »