Evolutionary Relationships and Fossils

The idea that all living things share a common ancestor and that differences between organisms are due to modifications that have occurred over time.

Scientific methods used to compare DNA, RNA, and proteins between species. More similar sequences indicate closer evolutionary relationships.

The process of comparing the sequence of DNA, RNA, or proteins to determine evolutionary relationships. More similarities indicate a closer evolutionary relationship between species.

Genes that have remained largely unchanged across different lineages. These genes are often critical for survival and reproduction.

The study of fossils to understand past life forms and environments. Fossils provide evidence for evolution and help reconstruct evolutionary relationships.

A series of fossil layers, with the oldest at the bottom and the youngest at the top. The fossil record provides insights into the history of life on Earth and the evolutionary changes across geologic time.

A proposed explanation for a phenomenon, often based on limited evidence. A hypothesis can be disproven but cannot be proven definitively.

A well-supported explanation for broad phenomena, backed by rigorous testing. Theories can be refined or modified but rarely overturned.

The time period in Earth's history before the Cambrian period, encompassing the Hadean, Archaean, and Proterozoic eons.

The current eon in Earth's history, characterized by the diversification of life and the emergence of complex organisms.

A major geological unit within an eon, often marked by significant changes in life on Earth.

The first eon in Earth's history, characterized by the formation of Earth and its early atmosphere.

The second eon in Earth's history, marked by the emergence of the first life forms, which were single-celled prokaryotes.

The third eon in Earth's history, characterized by the evolution of eukaryotes, multicellularity, and the first animals.

The first stage in the origin of life, characterized by the formation of simple organic molecules from inorganic matter.

The second stage in the origin of life, where simple organic molecules assemble into complex macromolecules such as proteins and nucleic acids.

The theory that RNA molecules were the primary carriers of genetic information and catalysts in early life, before the evolution of DNA and proteins.

The idea that protein molecules took over most catalytic roles from RNA as life evolved, due to their greater diversity and stability.

The theory that DNA replaced RNA as the primary carrier of genetic information because of its greater stability and suitability for long-term information storage.

A hypothetical scenario where life originated near deep sea vents, with mineral catalysts facilitating early metabolic reactions before nucleic acids and proteins formed.

A simple, self-contained structure formed by a lipid membrane surrounding a few macromolecules, representing a possible early stage of cell evolution.

The process by which protocells could divide without a cytoskeleton, possibly through mechanical forces like pore-extrusion.

The gradual change in the genetic makeup of a population over time, driven by mutation and other evolutionary mechanisms.

A collection of organisms that can interbreed and produce fertile offspring, evolving as a unit.

The early Earth's atmosphere was primarily composed of reducing gases like water vapor, nitrogen, carbon dioxide, and methane, but lacked significant amounts of oxygen.

These are geological formations on the ocean floor where hot, chemically-rich fluids emerge from the Earth's interior, providing a source of energy and chemical building blocks for life.

Proposed theories about how simple organic molecules, like amino acids, could have formed from inorganic molecules on the early Earth.

A famous experiment conducted in 1953 by Stanley Miller and Harold Urey, which simulated early Earth conditions and successfully produced amino acids from inorganic materials, supporting the idea that organic molecules could have formed naturally.

RNA molecules that possess catalytic activity, similar to enzymes. They serve as evidence supporting the RNA World Hypothesis, indicating that RNA could have both stored genetic information and catalyzed reactions in early life.

A hypothetical stage in the early evolution of life where RNA served as both the genetic material and the catalytic enzyme, potentially laying the foundation for the rise of DNA and proteins as key biomolecules.

Small-scale genetic changes within a population, often involving mutations, selection, drift, and migration. These processes are the foundation for larger evolutionary patterns.

Large-scale evolutionary trends resulting from accumulated microevolutionary changes. This includes the emergence of new species, major groups, and even entire phyla.

The complete disappearance of a species from Earth. It's a natural process, but can be accelerated by human activities.

A type of extinction where species disappear gradually over time due to natural processes like competition or environmental change.

A sudden and widespread extinction event that wipes out many species across the planet. Often caused by catastrophic events.

A rapid burst of diversification where new species develop rapidly to fill newly available ecological roles.

A model of evolution where change occurs gradually over long periods, with small changes accumulating over time.

A model of evolution where long periods of stability are punctuated by short bursts of rapid change.

Mitochondria and chloroplasts have similar structures to bacteria, including double membranes, ribosomes, size, and shape. This suggests an evolutionary relationship where these organelles originated from ancient bacteria.

The theory that mitochondria and chloroplasts evolved from ancient bacteria that were engulfed by eukaryotic cells. These bacteria became dependent on the host cell and eventually evolved into the organelles we see today.

A process where a cell membrane folds inward and forms a pocket that pinches off, creating an internal compartment. This is believed to have been involved in the formation of the nucleus and other internal membrane-bound organelles.

The ability of cells within a multicellular organism to specialize in different functions, leading to the development of tissues and organs. This is achieved through the selective expression of genes within the same genome.

A process where cells within a multicellular organism adhere to each other, creating physical connections. This is essential for forming tissues and organs.

Multicellular organisms arose independently at least 46 times in different lineages, including protists, fungi, plants, and animals. The transition from unicellular to multicellular life was a major evolutionary event.

Moving from an aquatic environment to land poses challenges such as maintaining water balance, supporting weight against gravity, and finding ways for reproduction.

The movement of organisms onto land from aquatic environments. This happened multiple times in different lineages, leading to the diversity of terrestrial life we see today.