BIO 1140 Lecture 1

What is the main goal of studying biology?

To discover and understand the underlying unity and diversity of life’s complex processes.

What are the key processes that make up life?

Growth, development, reproduction, metabolism, response to stimuli, adaptation, homeostasis, evolution, and cellular structure & function.

What is growth?

An increase in mass and size of an organism or organ.

How does an organism increase its mass?

By increasing cell number and cell size.

What is development?

The process where specialized cells arise from non-specialized cells.

What is cell differentiation?

The process of specialization of cells.

What causes cell differentiation?

Changes in gene expression.

What do all living things obtain from their environment?

Energy and raw materials (nutrients).

What happens to nutrients in the body?

They are broken down through biochemical reactions.

What does nutrient breakdown produce?

Building blocks for structures and energy for cellular work (mechanical, biochemical, electrical).

What is homeostasis?

The maintenance of a constant internal environment.

What is required for homeostasis?

Regulation of cell activity.

Give an example of homeostasis.

Regulation of blood sugar (glycemia) through insulin signaling.

What systems help maintain homeostasis?

Sensory, effector, and signaling mechanisms.

What do these systems do?

Detect changes (e.g., glycemia), send signals, and trigger responses (e.g., insulin secretion).

What is a mutation?

A permanent change in the DNA sequence.

What two processes explain the evolution of biodiversity?

Mutations and natural selection.

How do mutations affect a population?

They create differences among individuals.

Why are differences between individuals important?

They affect survival and reproduction chances.

What happens to the most adapted individuals?

They survive and reproduce (natural selection).

What does the word “cell” come from?

The Latin word cellula, meaning “small room.”

What is a cell?

A small membrane-bound unit filled with a concentrated aqueous solution of chemicals that can reproduce.

What do all cells have in common structurally?

A lipid membrane and similar organelles.

What are all living things made of?

Cells.

What types of molecules are common to all living things?

Carbohydrates, fatty acids, nucleic acids, and amino acids.

What do all living organisms share chemically?

The same 20 amino acids, lipids, sugars, and chemical groups.

What six elements make up most of life?

Hydrogen, carbon, nitrogen, oxygen, phosphorus, and sulfur.

Name common chemical groups found in living organisms.

Methyl, hydroxyl, carboxyl, carbonyl, phosphoryl, amino, and thiol.

Where is genetic information stored in cells?

In DNA (deoxyribonucleic acid).

What is DNA made of?

Four subunits called nucleotides.

What is a genome?

All the DNA in a cell.

What is a gene?

A segment of DNA that codes for a protein or RNA.

How does genetic information flow in a cell?

From DNA → RNA (transcription) → protein (translation).

Do all living things use genetic information the same way?

Yes, using an almost universal genetic code.

What do similarities among living organisms suggest?

They all share a common ancestor.

What is LUCA?

The Last Universal Common Ancestor.

When did LUCA likely exist?

Around 3.5 billion years ago.

What does LUCA represent?

The ancestral population from which all life descended.

What are protocells?

Precursors of cells formed when biological molecules became surrounded by a lipid membrane.

How did life first appear?

Through chemical evolution.

What does chemical evolution involve?

Formation of small organic molecules (amino acids, nucleotides) and macromolecules (proteins, nucleic acids).

What did protocells eventually give rise to?

LUCA, the ancestor of all life.

What two main cell types evolved from LUCA?

Prokaryotes (bacteria and archaea) and eukaryotes.

How did the nucleus and endoplasmic reticulum likely evolve?

By invagination of the plasma membrane.

How did mitochondria originate?

From an ancient aerobic prokaryote engulfed by a pre-eukaryotic cell.

How did chloroplasts originate?

From a photosynthetic prokaryote engulfed by a eukaryotic cell.

What theory explains the origin of mitochondria and chloroplasts?

Endosymbiosis.

What does photosynthesis allow organisms to do?

Capture energy from the Sun.

What major atmospheric change did photosynthesis cause?

Accumulation of oxygen (O₂).

What did increased oxygen lead to?

• Aerobic metabolism

• Formation of the ozone layer (O₃)

• Colonization of land

Why is aerobic metabolism important?

It is more efficient at extracting energy than anaerobic metabolism.

How did multicellular organisms likely evolve?

From aggregated eukaryotic cells.

What is the colonial hypothesis?

Single-celled eukaryotes stuck together in groups (colonies), and over time those groups became coordinated and specialized, eventually forming true multicellular organisms.

What are the three domains of life?

Bacteria, Archaea, and Eukarya.