Properties of Living Organisms

Cellular Organization

All living organisms are composed of cells, which are the basic units of life. Cells can be unicellular (single-celled organisms) or multicellular (organisms made of many cells).

• Cell: The smallest unit of life, capable of performing all life processes.

• Example: Bacteria are unicellular; humans are multicellular.

Common Properties of Life

Living organisms share several key properties that distinguish them from non-living matter.

• Order: Living things exhibit complex organization.

• Reproduction: Organisms reproduce their own kind.

• Growth and Development: Organisms grow and develop according to inherited instructions.

• Energy Processing: Organisms obtain and use energy to power activities.

• Response to Environment: Organisms respond to stimuli in their environment.

• Regulation (Homeostasis): Organisms maintain stable internal conditions.

• Evolutionary Adaptation: Populations evolve over generations.

Processing Energy

Autotrophs and Heterotrophs

Organisms process energy in different ways, classified as autotrophs or heterotrophs.

• Autotroph: An organism that makes its own food using carbon and energy from inorganic sources (e.g., plants via photosynthesis).

• Heterotroph: An organism that obtains food and nutrients by consuming other organisms (e.g., animals, fungi).

Formula for Photosynthesis:

Regulation: Homeostasis

Homeostasis refers to the ability of living things to maintain stable internal environments to optimize conditions for metabolism and other processes.

• Example: Human body temperature regulation.

Responding to the Environment and Evolutionary Adaptations

Response to Environment

Organisms interact with their environment, responding to external stimuli and changes.

• Example: Plants growing toward light (phototropism).

Evolutionary Adaptations

Adaptations are inherited traits that enhance an organism's ability to survive and reproduce in a particular environment.

• Example: Camouflage in animals.

Classification and Diversity of Life

Taxonomy: Classifying Life

Taxonomy is the science of classifying organisms. The diversity of life is organized into hierarchical categories.

• Levels of Classification: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

• Approximately 2 million species have been identified and named.

The Three Domains of Life

All life is classified into three domains based on cellular structure and genetics.

Unity and Diversity of Life

Cellular Similarity and Diversity

Despite the diversity of life, all organisms share fundamental cellular similarities, such as the presence of DNA and basic metabolic pathways.

• Example: Trees, fungi, and humans all have cells with similar structures.

Evolution: Evidence and Mechanisms

Concept of Evolution

Evolution is the process by which populations of organisms change over generations through mechanisms such as natural selection.

• Direct Observations

• Homology: Similarity due to shared ancestry.

• Fossil Record: Preserved remains or traces of organisms from the past.

• Biogeography: Geographic distribution of species.

Molecular Homology

Similarity in DNA, proteins, and other molecules among different species provides evidence for common ancestry.

• Example: All vertebrates have the gene for hemoglobin.

Fossil Record

The fossil record documents the existence, diversity, extinction, and change of many life forms throughout Earth's history.

• Shows evidence of descent with modification from common ancestors.

Natural Selection

Natural selection is the driving force behind evolution, favoring individuals with traits that enhance survival and reproduction.

• Populations contain organisms with varied traits.

• Individuals with certain traits survive and reproduce at higher rates.

• Natural selection increases the frequency of adaptations that are favorable in an environment.

• If the environment changes, natural selection may result in adaptation to new conditions or extinction.

Artificial Selection and Mutations

Humans can influence evolution through artificial selection, choosing specific traits to propagate. Mutations are changes in DNA that can introduce new traits.

• Artificial Selection: Selective breeding of plants and animals.

• Mutation: Any change in the DNA sequence.

Scientific Theory and Limitations

Nature of Scientific Theories

A scientific theory is a comprehensive explanation for a natural phenomenon, supported by a large body of evidence. Theories are not guesses; they are well-supported and predictive.

• Example: Theory of Evolution by Natural Selection.

Limitations of Science

Science has limitations; it cannot answer all questions, especially those outside the realm of observable phenomena.

• Supernatural and religious phenomena are beyond the scope of science.

• Science cannot solve all problems.

Darwin's Theory of Evolution

Darwin's Observations and Adaptation

Charles Darwin observed adaptation in organisms, such as finches on the Galápagos Islands, leading to the development of the theory of evolution by natural selection.

• Adaptation: Traits that improve survival and reproduction in a specific environment.

• Natural Selection: The gradual process by which heritable biological traits become more or less common in a population.

Key Vocabulary

• Eukaryotic cell

• Prokaryotic cell

• Heterotroph

• Autotroph

• Homeostasis

• Heredity

• Evolution

• Homology

• Mutation

• Adaptation

• Theory

• Artificial selection

Study Guide Questions

1. Name the 7 properties found in all living organisms.

2. Compare and contrast eukaryotic and prokaryotic cells.

3. Name the 3 domains of living organisms. Name the 6 kingdoms. Give examples of common organisms found in each.

4. Describe 3 different driving forces behind evolution.

5. Name 3 pieces of scientific evidence for evolution. Which plays the largest role in natural selection?

6. Using 1-2 sentences, link the terms: Natural Selection, Adaptation, and Evolution.

7. Give examples of species adaptations that Darwin noticed on the Galápagos Islands.

Additional info: Some explanations and examples have been expanded for clarity and completeness.