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

How Organisms Obtain Nutrients

Unicellular Organisms: Direct Nutrient Exchange

Unicellular living organisms perform nutrition by exchanging substances directly with their surrounding environment. Nutrients and oxygen enter the cell through a plasma membrane, through which waste is also expelled.

Multicellular Organisms: Systemic Nutrition

Multicellular living organisms, such as human beings, have most cells that do not come into direct contact with the outside world and cannot exchange substances with it directly. The nutrition function is performed through the joint action of different systems that act as intermediaries between the outside world and cells.

Essential Body Systems for Human Nutrition

The Digestive System: Nutrient Absorption

The digestive

Theories on the Origin of Life

The primordial soup hypothesis is incapable of explaining the origin of life because the early atmosphere wasn't composed of the gases described by Oparin and Haldane. Also, we know that in the early atmosphere, there was no ozone layer, so it would make the first molecules very unstable because of UV radiation. The hypothesis was supported by the Miller-Urey experiment, which consisted of the following: a mixture of gases was put in a container, and high-voltage electric shocks were applied. Then, gases were condensed in another container, simulating the primitive ocean. Finally, several organic compounds were found in that simulated "primordial soup," including amino acids. As an alternative to the primordial... Continue reading "Origin of Life and Evolution: Theories and Evidence" »

Respiration: The Energy Source of Life

Every living cell needs energy. In humans, our cells need energy for:

• Contracting muscles
• Making proteins
• Making new cells
• Cell division
• Producing heat inside the body

All of this energy comes from the food that we eat. The food is digested (broken down) and absorbed from the intestine into the blood. Then, the blood goes to the body, and the cells take the nutrients.

Aerobic Respiration

Most of the time, our cells release energy from glucose by combining it with oxygen.

Aerobic respiration involves chemical reactions in cells that use oxygen to break down nutrient molecules to release energy.

glucose + oxygen → carbon dioxide + water

Anaerobic Respiration

Anaerobic respiration involves chemical reactions in cells... Continue reading "Cellular Respiration: Aerobic vs. Anaerobic Processes" »

Chapter 1: Introduction to Cells and Microscopy

1.1 What are Living Things?

Organism: A living thing made up of cells.

Cell: The smallest living part of a living thing.

Unicellular: Single-celled organisms.

Multicellular: Organisms made of many cells.

Characteristics of All Living Things:

• Responds to its environment
• Needs energy
• Grows
• Reproduces
• Gets rid of wastes that build up in its body

Exploring the Microscopic World:

Compound Microscope: Combines two lenses to magnify objects.

Light Microscope: Uses light to view an object.

Resolving Power: The ability of a microscope to focus on two objects or details that are close together.

Magnification Power: The ability of a microscope to make an object appear larger.

Eyepiece: The lens you look through to magnify... Continue reading "Exploring the Microscopic World: Cells, Organelles, and Cellular Processes" »

Human Reproduction & Sexuality

Human reproduction is sexual and has two key characteristics:

• The new individual is formed from a single cell called a zygote.
• Zygotes result from the union of two gametes (fertilization).

Humans have two types of gametes: sperm (men) and ova (women).

Changes During Reproductive Life

During the reproductive life of a human being, there are three main stages:

• Puberty

  Puberty begins in men with the first ejaculation (spermarche) and in women with the first menstruation (menarche). This is due to the increased secretion of pituitary hormones: Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH), which stimulate gamete production.

  Puberty typically begins when girls are 10-13 years old and boys 12-14. It lasts

DNA Mutations

Mutations are alterations to a DNA sequence that occur when a gene is damaged or changed, altering the genetic message. These mutations can have varying effects on health, depending on their location and whether they alter essential protein functions.

Mutations can occur at three levels:

1. Molecular (Gene or Point)
   • These mutations affect the chemical constitution of genes, specifically the DNA bases.
2. Chromosomal
   • These mutations affect a segment of a chromosome, altering its structure through deletions, duplications, or rearrangements.
3. Genomic
   • These mutations affect the entire genome, altering the number of chromosome sets (polyploidy or haploidy) or individual chromosomes (e.g., trisomy 21).

Mutations can be of different types:

1. Gene Mutations:

Digestive Phases

Cephalic Phase

The cephalic phase initiates digestion before food even reaches the stomach. Sensory cues like taste, smell, or even the thought of food trigger the central nervous system to stimulate gastric juice production.

Gastric Phase

Once food enters the stomach, receptors signal the brain, which in turn promotes further gastric juice secretion to break down the ingested food.

Intestinal Phase

As food moves into the duodenum, receptors detect its presence and signal the brain to increase the production of digestive juices for further processing.

Enterogastric Reflex

When the duodenum is full, the enterogastric reflex is activated, causing the pyloric sphincter to close and regulate the passage of chyme from the stomach to the... Continue reading "Digestive System Processes: A Comprehensive Guide" »

Lower First Premolar

Prominent Elevations & Depressions/Snake-Snail Eye Lingually

Chronology

• Enamel: 5-6 years old
• Eruption: 10-11 years old
• Root: 12-13 years old

Geometry

• Lingual/Buccal: Trapezoid; short side cervical
• Mesio-Distal: Rhomboidal
• Occlusal: Diamond

Buccally

• Cervical Ridge
• Buccal Ridge
• Mesio-Distal Buccal Developmental Groove

Lingually

• Mesio-lingual Developmental Groove

Mesially

• Mesio-lingual Developmental Groove

Mesial Contact Area

• Junction between buccal and middle thirds

Distal Contact Area

• Middle third

Occlusally

• 2 well-developed cusps
• Each cusp: triangular ridge
• Mesial/Distal Marginal Ridges
• Triangular Fossae
• Developmental Pits
• Central Developmental Groove
• Transverse Ridge
• Mesio-lingual Developmental Groove

Lower Second Premolar

3-Cusp Type has 5 Lobes