Chapter 1 Principles of Life – Key Concepts (1.1, 1.2, 1.4)

A set of question-and-answer flashcards covering the key concepts from Chapter 1: Principles of Life (sections 1.1, 1.2, and 1.4), including definitions, evolutionary theory, origin of life, organization and energy, and the tree of life.

What is biology?

The scientific study of living things or organisms.

Do viruses count as living organisms?

Most biologists consider them part of life, though the living/non-living distinction is not always clear.

What common feature do all living organisms share in terms of structure?

They are composed of a common set of chemical components and similar structures, notably cells.

What kind of genetic code do living organisms use?

A nearly universal genetic code.

What do living organisms do with molecules obtained from their environment?

They convert environmental molecules into new biological molecules.

How do living organisms obtain and use energy?

They extract energy from the environment and use it for life functions.

How is genetic information propagated during reproduction?

Genetic information is replicated in the same manner when reproducing.

How does evolution occur at the genetic level?

Through gradual changes in genetic information.

When did Earth form and when did the earliest life likely evolve?

Earth formed about 4.6–4.5 billion years ago; earliest life evolved about 600 million years after that.

What was a critical step for the evolution of life?

The formation of nucleic acids capable of reproducing themselves and containing information to make proteins.

What development followed the formation of nucleic acids in early life?

Biological molecules became enclosed in a membrane to form a cell.

What role did fatty acids play in early cells?

They formed membranes that separated cells from their surroundings.

What advantage did a cell interior provide?

Concentrated reactants and products allowed reactions to be integrated and controlled.

How long did unicellular prokaryotes dominate life on Earth?

About 2 billion years.

When did photosynthesis evolve and what did it accomplish?

About 2.7 billion years ago; it converted sunlight into chemical-bond energy in biological molecules.

What was the by-product of early photosynthesis and its atmospheric effect?

Oxygen (O2) was produced and began to accumulate in the atmosphere.

Why did some early prokaryotes struggle with oxygen, and what metabolism evolved?

O2 was poisonous to many, so organisms that could tolerate O2 evolved aerobic metabolism, which is more efficient than anaerobic metabolism.

What atmospheric change allowed life to move from sea to land?

The formation of an ozone (O3) layer that absorbs UV light, enabling land colonization around 500 million years ago.

What are eukaryotic cells characterized by?

Membrane-enclosed organelles and a nucleus; prokaryotes lack a nucleus and other internal compartments.

When did multicellular eukaryotes likely arise and why?

About 1 billion years ago, due to cellular specialization that allowed larger, more adaptable organisms.

What does binomial nomenclature refer to and give an example?

A two-part scientific name; for example, Homo sapiens.

What do phylogenetic trees depict?

Evolutionary relationships among organisms as part of a tree of life.

What are the three domains of life?

Bacteria, Archaea, and Eukarya.

From which group did Eukarya arise, and what contributed organelles?

Eukarya arose from Archaea, with mitochondria and chloroplasts contributed by endosymbiotic bacteria.

What is the concept of Organization & Energy in life?

Life depends on a hierarchy of organized levels from molecules to ecosystems; cells use energy to synthesize complex molecules, and organization is essential for function in multicellular organisms.

What is a biological system?

A set of interacting parts where the behavior of the whole depends on interactions among parts.

At what levels do organized systems exist?

At cellular, organismal, and community levels, among others.

What is positive feedback in biological systems?

A process where a product speeds up an earlier process, tending to destabilize the system (e.g., lactation).

What is negative feedback in biological systems?

A process where a product slows down an earlier process, helping stabilize the system (e.g., regulation of blood glucose).

How is evolution defined in this course?

A change in the genetic makeup of biological populations through time.

What mechanism explains how evolution creates adaptations?

Natural selection leading to adaptations—traits that enhance survival and reproduction.

What are adaptations?

Structural, physiological, or behavioral traits that improve an organism’s chances of survival and reproduction.

How can evolution be observed and measured?

Through changes in genetic composition of populations over short time frames and the fossil record over long time frames.