Characteristics of Life

Characteristics of Life

• Biology is the scientific study of life.
• Life is defined by shared characteristics among all living organisms.
• Living organisms exhibit levels of organization, acquire materials and energy, and maintain an internal environment.
• Organisms respond to stimuli, reproduce, develop, adapt, and evolve in changing conditions.
• Studying these characteristics helps differentiate between living and nonliving things.

Levels of Organization

• Atoms are the basic units of matter.
• Atoms combine to form small molecules, which join to form larger molecules within a cell.
• Cells are the smallest, most basic unit of life.
• Similar cells combine to form tissues.
• Tissues make up organs; various tissues combine to form organs, like the heart or a leaf.
• Organs work together in organ systems, such as the cardiovascular system.
• A species is a group of similar organisms capable of interbreeding.
• A population includes all members of a species in a particular area.
• A community is formed when different populations interact.
• At the ecosystem level, communities interact with the physical environment.
• The biosphere encompasses all ecosystems on the planet.

Tissue

• Tissue is an ensemble of similar cells from the same origin performing a specific function, organized between cells and a complete organ.
• Animal tissues include connective, muscle, nervous, and epithelial tissues.
• Plant tissues include vascular, ground, and epidermal tissues.
• Organs are formed by the functional grouping of multiple tissues.

Organ & Organ Systems

• Organs are collections of tissues forming a functional unit specialized to perform a particular function.
• Examples of organs are the heart, kidneys, and lungs.
• Organs lie between tissue and an organ system in the hierarchy of life.
• Organ Systems are composed of functionally related organs working together to perform functions.
• Each organ has a specialized role and is made up of distinct tissues.
• Examples of organ systems include the respiratory, digestive, circulatory, endocrine, and lymphatic systems.

Life's Energy and Matter Requirements

• Various cellular activities, like moving, growing, and reproducing, require energy.
• Energy is the capacity to do work.
• Food provides nutrient molecules used as building blocks or energy sources.
• Cells use nutrient molecules to carry out chemical reactions.
• Metabolism includes all chemical reactions occurring in a cell.

Metabolism: Anabolism and Catabolism

• Energy in food must be converted to cellular energy.
• Building blocks for proteins include lipids, carbohydrates, and nucleic acids.
• Metabolic wastes are eliminated.
• Catabolic reactions break down compounds, releasing energy.
• Anabolic reactions build up compounds, consuming energy.

Homeostasis

• Homeostasis is the maintenance of stable internal conditions, such as temperature, moisture level, and acidity (pH), necessary for metabolic processes.
• Living organisms must keep themselves stable for metabolic processes to continue.

Response to Stimuli

• It is how living organisms find energy and/or nutrients by interacting with their surroundings.
• Multicellular organisms can manage more complex responses.
• Responding often results in movement.
• Appropriate responses help ensure survival, are essential for daily activities, and are overall defined as "the behavior of the organism".

Reproduction and Development

• New life only comes from existing life.
• Every living organism can reproduce or make another organism like itself.
• Single-celled organisms split into two.
• Multicellular organisms reproduce by pairing a sperm and an egg.
• The union of sperm and egg results in an immature individual that grows and develops through various stages to become an adult.

The Cell

• A cell is the smallest unit of living things and the basic unit of life.
• Cells display all characteristics of life.
• A cell contains energy, genetic information, and structures.

Functions and Cell Specialization

• Cells can reproduce, grow, respond to stimuli, and use energy.
• Some cells have specialized functions like muscle cells containing proteins or red blood cells containing hemoglobin.
• There are about 260 different cell types in the human body.
• Cell specialization results because of differences in gene expression.

Chemical Constituents and Microscopy

• Cells are too small to be seen without magnification.
• The development of cell biology depended on the invention of the microscope.
• Cell biology began with the light microscope.

Discovery of Microorganisms

• Robert Hooke (1635-1703) was an English mathematician and naturalist and an excellent microscopist.
• Hooke's book Micrographia (1665) was the first book devoted to microscopic observations.
• Hooke illustrated fruiting structures of mold.
• Hooke named cells "cellula" (small room).
• Hooke gave the first known description of microorganisms.
• Hooke did not realize the importance of the observation.

Leeuwenhoek and Spontaneous Generation

• Antoni van Leeuwenhoek (1632-1703) was the first person to see bacteria.
• Leeuwenhoek was an amateur microscopist.
• Leeuwenhoek constructed a simple microscope with a single lens to examine substances for microorganisms.
• He had high magnification with the simple microscope.
• He could not see the reproduction of cells.
• He continued to believe in the idea of spontaneous generation ("Life arises from the nonliving or from nothing").

Simple and Modern Microscopes

• Simple microscopes use a single lens to magnify objects up to 300X using natural light illumination from the bottom.
• Modern microscopes contain illumination, imaging, and magnification systems.
• Modern microscopes use artificial light and lens to shape and filter light.
• Modern microscopes have shaping, contrast, and resolution.
• Modern microscopes improves visibility using filters.

Understanding Microscope Properties

• Employ lenses to magnify the image.
• The total magnification is the product of the objective and ocular lens magnifications.
• Light microscopes have an upper magnification limit of 2000X.
• Immersion oil increases light-collecting ability.
• Resolution is the ability of a microscope to distinguish two adjacent objects distinctly.
• The smallest cellular structure visible with a light microscope is a mitochondrion.

Light Microscopy

• Light microscopes illuminate cell structures using visible light.
• Types of light microscopes include bright-field, phase-contrast, differential-interference contrast, dark-field, and fluorescence microscopes.

Staining

• Dyes increase cell contrast for better visibility.
• Dyes are organic compounds with an affinity for specific cellular material.
• Iodine can stain plant cells.
• Hematoxylin and eosin (H&E) stains the nucleus purple and other tissue components pink.

Cell Theory Foundation

• The cell is the fundamental unit of life emerged.
• Its emergence was delayed until the 19th century due to poor technology, crude microscopes, and a lack of procedures when preserving and studying living cells.

Cell Theory: Development

• In the 19th century, more powerful microscopes revealed details of life at the subcellular level.
• The nucleus was identified as a darkened area in plant and animal cells in the 1830s.
• Cytoplasm was identified as the remaining cell material.
• Matthias J. Schleiden and Theodor Schwann developed cell theory around 1839.
• Schleiden noted that cells were the basic units of plant cells.
• Schwann compared animal cells to plant cells.

The Principles of the Cell Theory

• Cells are the elementary particles of organisms and the unit of structure and function.
• The cell components as a cell body and nucleus are contained within a surrounding membrane.
• Schleiden called a cell a "peculiar little organism" and realized that a cell can be a living entity on its own
• In plants and animals, cells are part of a larger living organism
• Rudolph Vickhow noted all cells come from preexisting cells.

Classification of Living Things

• The broadest classification is the domain.
• Domains include Archaea, Eubacteria (Prokaryote), and Eukaryota.
• Kingdoms include Plants, Animals, Fungi, Protists (Eukaryote), Eubacteria (Monera), and Archeabacteria (Prokaryote).

Prokaryotes and Eukaryotes

• Comparative rRNA sequencing shows three distinct cellular lineages.
• The domains are Bacteria, Archaea, and Eukarya.
• Archaea are more closely related to Eukarya than Bacteria.

Habitats of Prokaryotes

• Prokaryotes live in all ecosystems.
• Prokaryotes are on plants and animals, in the soil, in depths of the oceans
• Prokaryotes are in extreme cold, in extreme hot, and in extreme salt
• Prokaryotes are on the living org. and on the dead org

Characteristics of Prokaryotic Cells

• Prokaryotic cells have no membrane-bound nucleus.
• The nucleoid is the region of DNA concentration.
• Organelles are not bound by membranes.

Prokaryotic Cell Components

• Prokaryotic cells contain cytoplasm, ribosomes, and a nuclear zone.
• Prokaryotic cells contain DNA, plasmids, a cell membrane, and a cell wall.
• Prokaryotic cells contain a capsule (or slime layer) and flagellum.

Differences Between Bacteria and Archaea

• Archaea is closer to eukaryotes regarding how genetic information is handled.
• Bacteria is closer to eukaryotes in terms of metabolism and energy conversion.

The Uses of Prokaryotyes

• Prokaryotes are used in many biotechnological applications because of their ability to survive in the most extreme environments.
• Their features make them suitable for use as model organisms in genetic research
• They are useful in biochemical, ecological and commercial processes such as: – Food processing – Sewage treatment – Oil spill cleanup – Nitrogen, sulfur and Carbon dioxide cycling – Antibiotic production
• They are not harmful to their hosts

Classification fo Eukaryotic Cells

• Protist: unicellular eukaryotes -Examples: amoeba; algae
• Fungi include: -Examples: yeast; mold; mushroom
• Plant Cells
• Animal Cells

Eukaryotic Cells Components

• Eukaryotic Cells contain Cytoplasm, Nucleus, Mitochondria, Chloroplast, Ribosomes, Golgi body, Vacuoles Lysosomes, Cytoskeleton, Centriole, Cilium and Flagellum, Microvilli, Cell membrane and Cell Wall

What Prokaryotic and Eukaryotic Cells Have in Common

• Both cell types have DNA as their genetic material.
• Both cell types are covered by a cell membrane.
• Both cell types contain RNA.
• Both cell types are made from the same basic chemicals, i.e. Carbohydrates, proteins, nucleic acids, minerals, fats, and vitamins
• Both cell types have ribosomes, regulate the flow of the nutrients and wastes that enter and leave them, have similar basic metabolism like photosynthesis and reproduction
• Both call types require a supply of energy.