Intro to the Study of Life

• The scientific study of life covers what life is, the tree of life, and how scientists study the natural world.

What is Life?

• Biology is the study of life.
• Living organisms can be unicellular or multicellular.
• The cell membrane separates organisms from their surroundings.
• Five fundamental qualities constitute life.

Characteristics of Life

• Organization: Atoms make up molecules, which form cells, then tissues, and so on.
• Energy Use: A kitten uses its mother's milk for energy to fuel its own growth.
• Maintenance of Internal Constancy (Homeostasis): Kidneys regulate body water balance by adjusting urine concentration.
• Reproduction, Growth, and Development: An acorn germinates, develops into a seedling, grows, and reproduces sexually.
• Evolution: Increasing numbers of bacteria survive treatment with antibiotics.

Life's Organizational Levels

• Living things are organized from microscopic to macroscopic levels.
• Levels range from atoms, molecules, and cells to organisms, populations, communities, and the biosphere.
• Each level is more complex than the preceding one.
• Each level has all the properties of the previous level.
• Higher levels emerge through interactions between components on lower levels.

Life Requires Energy

• Maintaining organization and conducting life-sustaining processes requires energy.
• The sun is the ultimate source of energy.
• Plants capture solar energy and carry out photosynthesis.
• Photosynthesis transforms solar energy into chemical energy (organic molecules).
• Other organisms use chemical energy.
• Metabolism includes all the chemical reactions in a cell or in an organism.
• Homeostasis maintains internal conditions within certain boundaries, like temperature, moisture, and pH.

Living Things Respond to Stimuli

• Living things interact with the environment and respond to changes.
• All living things exist linked and dependent on each other.
• Response ensures survival and often results in movement.

Life Reproduces, Grows, and Develops

• Reproduction transmits DNA from one generation to the next.
• Reproduction can be asexual or sexual.
• Asexual reproduction involves DNA from one parent, offspring are identical to the parent.
• Sexual reproduction involves DNA from both parents, resulting in a new combination of traits.

Sexual Reproduction and Genetic Diversity

• Sexual reproduction enhances chances of survival when conditions change.
• Sexual reproduction is a very successful strategy.
• Sexual reproduction is common among plants, animals, and fungi.

Life Evolves and Adapts

• Adaptation is an inherited characteristic or behavior.
• Adaptations enable organisms to survive and reproduce in a given environment.
• Natural selection enhances the reproductive success of certain individuals from a population based on inherited characteristics.
• Evolution results in a change in the genetic makeup of a population over multiple generations.
• Charles Darwin became famous in the 1860s after publishing The Origin of Species by Means of Natural Selection.
• Darwin's book introduced the theory of evolution by natural selection.
• Evolution explains the current diversity of life.
• Similarities among existing organisms suggest species come from a single common ancestor.

The Tree of Life's Three Main Branches

• The Tree of Life in science divides all living things into three domains.
• These three domains are Bacteria, Archaea, and Eukarya.

Taxonomy

• Taxonomy is the science of naming and classifying organisms.
• The species is the basic unit of classification.
• Closely related species are grouped in the same genus.
• The genus and specific descriptor form the unique, two-word scientific name, like Homo sapiens.
• Binomial nomenclature is the modern system of taxonomy.
• According to binomial nomenclature, each species has 2 names (scientific name).
• A genus is a group of similar species.
• Latin used to be the language used to name species.
• Genus name is always capitalized.
• Species name is always lowercase.
• Both names must be underlined (hand written) or italicized (typed).

Domain Archaea

• Archaea are mostly unicellular cells of various shapes.
• Archaea lack nuclei.
• Archael cells can adapt to extreme environments.
• Archaea are characterized by unique chemical properties.

Domain Bacteria

• Bacteria are mostly unicellular cells of various shapes.
• Bacterial cells lack nuclei.
• Bacterial cells can adapt to extreme environments.
• Bacteria are characterized by unique chemical properties.

Domain Eukarya

• Eukarya contain cells with nuclei (eukaryotic).
• Eukarya can be unicellular or multicellular.
• Protista can be unicellular or multicellular and autotrophic or heterotrophic.
• Kingdom Animalia is multicellular and heterotrophic by ingestion.
• Kingdom Fungi is mostly multicellular and heterotrophic through external digestion.
• Kingdom Plantae is multicellular and autotrophic.

Biodiversity

• Biodiversity is the total number of species on earth, the variability of their genes, and the different ecosystems they live in.
• It is estimated that for every 1 species described, there are 2 undescribed.
• There are about 1.2 million species described to date.
• Extinction is the death of the last member of a species with an estimated 150 species lost per day.
• Humans depend upon healthy ecosystems.
• Ecosystems are impacted by human populations through means such as destruction, degradation and exploitation.