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

Fundamental Ecological and Biological Concepts

Biodiversity: The Variety of Life

Biodiversity refers to the varying or different life forms found on Earth. It encompasses several types:

• Genetic Diversity: The variety of genetic materials within a species or a population.
• Species Diversity: The number and abundance of species present in different communities.
• Functional Diversity: The biological and chemical processes, such as energy flow and matter recycling, needed for the survival of species, communities, and ecosystems.
• Ecological Diversity: The variety of terrestrial and aquatic ecosystems found in an area or on the Earth.

Evolution: Changes in Organism Genetic Makeup

Evolution refers to the changes in a population of organisms' genetic makeup... Continue reading "Essential Concepts in Ecology and Environmental Science" »

Human Nutrition and Body Systems

The digestive, respiratory, excretory, and circulatory systems all play a role in nutrition.

• Digestive system: Introduces foods into the body, and prepares and transforms it to enable its use by cells.
• Respiratory system: Obtains the oxygen cells need and eliminates carbon dioxide produced during cell metabolism.
• Circulatory system: Transports nutrients and oxygen to cells and releases waste substances.
• Excretory system: Releases waste substances outside the organism.

The Digestive System: Function and Structure

The digestive system breaks nutrients into parts small enough for your body to absorb and use for energy, growth, and cell repair. It is made up of the gastrointestinal (GI) tract and the accessory glands:... Continue reading "Human Digestive System: Organs, Functions, and Processes" »

Essential Concepts in Biology and Heredity

Fundamental Definitions in Genetics

Gene

The basic unit of heredity passed from parent to child. Genes are made up of sequences of DNA and are arranged, one after another, at specific locations on chromosomes in the nucleus of cells.

Codominance

Codominance, as it relates to genetics, refers to a type of inheritance in which two versions (alleles) of the same gene are expressed separately to yield different traits in an individual.

Cellular Components and Principles

Ribosomes

Small particles with two subunits, without membranes to divide them. They are responsible for building proteins using the information coded in a linear molecule of nucleic acid (RNA).

Mendel's Second Law of Segregation

Mendel's second law... Continue reading "Cell Biology and Genetics: Core Definitions and Principles" »

The Human Digestive System: Function and Components

The digestive system transforms food into nutrients, which are then transported by the circulatory system through the blood to the cells. It is a set of organs and structures, including the digestive tract and accessory glands.

Key Components of the Digestive System

• Mouth
• Pharynx
• Oesophagus
• Stomach
• Small Intestine
• Large Intestine
• Appendix
• Salivary Glands
• Liver
• Pancreas

Initial Digestion: Mechanical and Chemical Processes

Digestion is the transformation of food into nutrients so that cells can benefit from them. It can be mechanical or chemical. Digestion begins in the mouth immediately after food is ingested.

Processes and Elements in Oral Digestion

• Mastication (Chewing)
• Food
• Tongue
• Salivary Glands
• Bolus formation

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" »