Prokaryotes vs. Eukaryotes: Cell Structure, Function & Differences
Eukaryotes vs. Prokaryotes
- Organelles:
- Unique to Prokaryotes:
- Nucleoid: Region containing genetic material (DNA), lacks a membrane. Allows for rapid gene expression.
- Cell Wall: Provides structural support, protects against osmotic pressure changes, and helps maintain cell shape. Composition varies among bacteria (peptidoglycan in most).
- Plasmid: Small, circular DNA molecule separate from the chromosomal DNA. Often carries accessory genes, like antibiotic resistance. Facilitates horizontal gene transfer.
- Unique to Prokaryotes:
Energy Flow and Nutrient Cycles in Ecosystems
Energy Flow in Ecosystems
The sun is the principal source of energy input to biological systems. Energy flow is not a cycle. It starts from the sun and then that energy is harnessed by plants, which are eaten by animals, which are eaten by other animals. At each step, energy is lost to the environment (for example, by heat loss).
Food Chains and Food Webs
Food chain: A chart showing the flow of energy (food) from one organism to the next, beginning with a producer.
Food web: A network of interconnected
Read MoreCommon Diseases: Causes and Prevention
Diseases: The appearance of diseases in the systems and organs involved in nutrition is highly variable. They are caused by:
- Inadequate food consumption.
- Consumption of harmful substances such as tobacco, alcohol, and drugs.
- Lack of moderate physical exercise.
- Emotional stress.
Medicine helps to prolong human life.
Cardiovascular Diseases
Atherosclerosis: Results from the accumulation of cholesterol in blood vessel walls, leading to atheroma. When blood vessels narrow and blood circulation is impaired,
Read MoreBiology Review: Key Concepts and Answers
- Vaccines are used to introduce weakened or dead pathogens to stimulate the: immune system to react and be ready to fight future invasions by these microbes
- Which structure is closed or blocked to prevent sperm from traveling from the testes to the urethra in a vasectomy? A
- Sweat and skin secretion kill or limit the growth of many types of microbes. This control of microbes is an example of: a non-specific immune response against infection
- The fluid-filled structures in which the embryo is protected
Science Fundamentals: Key Concepts and Definitions
Science Fundamentals: Key Concepts
Science is a body of knowledge and a process for generating that knowledge.
The Scientific Method
What is science and the scientific method based on? Evidence
An observation is a description, measurement, or record of any object or scientific phenomenon.
After it has been supported by a predictable experimental outcome, a scientific hypothesis still cannot be considered to have been proven true.
In a controlled experiment, which variable is manipulated? Independent variable
Basic
Read MorePlate Tectonics: Shaping Earth’s Crust
The study of the processes that shape the broad outlines of the Earth’s crust through the creation of continents and oceans, mountains and sea trenches, and so on.
The plates are pieces (more or less rigid) in the most superficial part of the Earth that move about with respect to others. For example, imagine chunks of melon peel slipping on the fruit’s flesh. The interactions between these plates result in tectonic processes. The theory of plate tectonics elegantly explains a wide range of geological,
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