Intro to Biology: Characteristics of Life

• Biology is defined as the science of life and living organisms.
• All living things are composed of cells.
• Organisms can be unicellular or multicellular.
• The first life form appeared 3.5 billion years ago.
• The earliest evidence of life occurs in microfossils, which are the remains of tiny plants and animals.
• The prevailing theory among scientists is that life originated from inanimate objects.
• Life is characterized by structure, function, growth, origin, evolution, and distribution.
• Cell theory, evolution, genetics, and homeostasis, are unifying principles in biology.
• Biologists study the diversity of life, research diseases, develop technologies, improve agriculture, and preserve the environment.

Eight Characteristics of Life

• Living things are made up of cells, which serve as the basic structural and functional units.
• The levels of organization are atoms, molecules, cells, tissues, organs, organ systems, and organisms.
• Atoms are arranged into molecules, molecules into macromolecules, which organize into organelles that work together to form cells.
• DNA, the genetic code, is present in every cell.
• Living organisms respond to their environment by sensing and reacting to changes.
• Adaptation is the process of adjusting to an environment influenced by structural, physiological, and behavioral traits improving survival and reproduction.
• Plants exhibit tropism including thigmotropism (touch), phototropism (light), hydrotropism (water), geotropism (gravity), and thermotropism (temperature).
• Homeostasis maintains a stable internal condition.
• A normal human temperature ranges from 36-37 degrees Celsius.
• Metabolism is the sum of all chemical reactions in a cell.
• All metabolic reactions convert energy.
• Catabolism breaks down substances, releasing energy.
• Anabolism uses energy.
• Plants and bacteria are independent producers or autotrophs that make their own food.
• Plants are phototrophs, using light for energy.
• Bacteria are chemotrophs, using chemicals for energy.
• Humans and animals are consumers or heterotrophs dependent on other organisms.
• All living things grow and change, whereas bacteria multiply instead of growing.
• Reproduction is the process of making the next generation.
• Asexual reproduction involves no fertilization, no sex cells, and only a single parent cell.
• Budding is a form of asexual reproduction in which small growths on the parent organism's surface break off.
• Cloning replaces an embryonic cell's DNA.
• Sexual reproduction involves fertilization, which is the union of gametes from female and male organisms.
• Adaptation is the ability to survive.
• Evolution is ever changing because of adaptation.
• A scientific theory is an explanation of natural phenomena supported by many observations and experiments over time.
• Peer review involves evaluating experimental procedures and results by other scientists.

Cell Theory

• Robert Hooke discovered cells in 1665 while observing a thin slice of cork.
• He described cells as tiny boxes or a honeycomb.
• Hooke believed cells only existed in plants and fungi.
• Anton van Leeuwenhoek discovered single-celled organisms in 1673, which he termed "animalcules."
• Blood cells observed from fish, birds, frogs, dogs, and humans. Spontaneous generation (abiogenesis) suggests life originated from non-living organisms.
• Louis Pasteur disproved spontaneous generation in the 19th century.
• Matthias Schleiden concluded that all plants are made of cells (1838).
• Theodor Schwann stated that all animal tissues are made of cells (1839).
• Rudolf Virchow concluded that cells must arise from pre-existing cells (1858).

Cell Theory (Components)

• Organisms are composed of one or more cells.
• The cell is the basic unit of life in all living things.
• Cells are produced by the division of pre-existing cells.
• Cells contain DNA passed on from cell to cell during cell division.
• Cells are the same in chemical composition and metabolic activities.
• All basic chemical and physiological functions are carried out inside the cell.
• Cell activity depends on the activities of sub-cellular structure within the cells.
• The scientific method is a systematic process used to answer questions and solve problems.

The Scientific Method (steps)

• Question: Specific and based on an observation.
• Background research: Research helps make informed predictions and ensures work isn't repeated.
• Hypothesis formation: an educated guess about the answer to your question (if-then statements).
• Experiment: Tests hypothesis.
• Involves an independent variable (what you change).
• Involves a dependent variable (what you measure).
• Record and analyze: Collect data and record observations for hypothesis support.
• Drawing conclusions: Decide if hypothesis was correct.
• Drawing a conclusion helps reflect on learning and how the experiment might be improved.
• Communicating results.

Cell Organelles

• Cell shape, structure, and function maintain system activity.
• Cells contain functional structures called organelles.
• Organelles are tiny structures within the cell, functioning like the body's organs.
• Each organelle has a specific job to help the cell survive and function:
• The Nucleus is a membrane-bound organelle containing DNA (deoxyribonucleic acid) within chromosomes.
• Mitochondria are membrane-bound organelles where chemical energy production (ATP- Adenosine triphosphate) occurs.
• The Cell Membrane provides protection and supports homeostasis by regulating the materials that enter and exit the cell.
• The Golgi Apparatus is a membrane-bound organelle that packages proteins and lipids (fats) into vesicles for transport.
• Smooth ER does not have ribosomes and produces lipids (fats).
• Rough ER has ribosomes and produces proteins.
• Vacuoles are membrane-bound organelles supporting cell storage and waste management.
• Plant cells have larger vacuoles for food and water storage.
• Chloroplasts are membrane-bound organelles where photosynthesis occurs.
• Chloroplasts transform light energy into chemical energy.
• Chloroplasts are only present in plant cells

Eukaryotic vs Prokaryotic Cells

• Eukaryotic and Prokaryotic cells are very different
• Prokaryotic Cells are the simplest type of cell
• Pro means before and Karyon (kernel) means nuclei
• The oldest type of cell, they appeared about four billion years ago.
• They are the largest group of organisms.
• All prokaryotic organisms are unicellular.
• Prokaryote's organelles have coverings known as membranes.
• Represented by ancient bacteria and archaea (extreme environments).
• Thermophiles thrive in hot environments.
• Mesophiles thrive in moderate temperature.
• Halophiles thrive in cold environments.
• Acidophiles thrive in acidic environments.
• Prokaryote Shapes:
• Cocci: spherical (round)
• Bacillus: rod-shaped
• Spirilla: helical (spiral)
• Eukaryotic Cells meaning:
• Eu means true and Karyon (kernel) means nuclei
• More advanced than prokaryotes.
• The nuclear membrane surrounds linear genetic material (DNA).
• Have several different parts and a complex internal structure.
• Larger in size.
• Can be unicellular or multicellular.

Eukaryotic vs Prokaryotic Cells (differences)

• Prokaryotic cells lack a membrane around their organelles whereas Eukaryotic cells have a membrane
• Prokaryotic cells only have ribosomes for organelles vs Eukaryotic cells which have multiple organelles with ribosomes
• Genetic material floats in the cytoplasm (DNA and RNA) in Prokaryotic cells, vs Membrane-covered genetic material in Eukaryotic cells
• Prokaryotic cells have circular DNA vs Linear DNA in Eukaryotic cells
• Prokaryotic cells are unicellular whereas Eukaryotic cells are either unicellular or multicellular
• Prokaryotic cells are smaller in size vs Eukaryotic cells being larger in size
• Prokaryotic cells have a larger number of organisms vs Eukaryotic cells with smaller number of organisms
• Prokaryotic cells appeared 4 billion years ago vs Eukaryotic cells which appeared 1 billion years ago

Eukaryotic vs Prokaryotic Cells (Similarities)

• Eukaryotic and Prokaryotic Cells both:
• Have a cell membrane (outer covering of the cell)
• Have Ribosomes
• Have DNA
• Have a cytoplasm (liquid environment)