Tempo of Evolutionary Change

Gradualism

New species arise from a gradual transformation of an ancestral species through slow, steady change.

Punctuated equilibrium

The majority of the time, a lineage is in stasis. Major change occurs rapidly and from branching lineages

Anagenesis

gradual modification through time, eventually reaching a recognizable different morphology

Cladogenisis

when an ancestral species branches into two or more descendant species (can happen due to allopatry)

Adaptive Radiation

an evolutionary lineage that has undergone exceptionally rapid diversification into a variety of lifestyles or ecological niches

Key Innovation

emergence of new traits within a clade

Cambrain Explosion

• Sudden appearance of animal body forms in the fossil record.

• The earliest fossils of most living animal phyla

• The simultaneous appearance is one of the most important macroevolutionary events in the history of life.

Triggers

• Sea level rose, submerging land and allowing colonization

• inc. calcium levels resulting in the development of shells to prevent poisoning.

Background extinction

The normal rate of extinction for a taxon or biota. (~0.1-2 species lost/million species/year)

Mass Extinction

A statistically significant increase in extinctions above background extinction rates.

Large Igneous Provinces

Earth cracks open, pushing vast amounts of molten rock to the surface— it can last for thousands or millions of years.
vast stretches of fresh rock

Distinguish between gradualism and punctuated equilibrium, as wall as anagenesis and cladogenesis

• Gradualism: New species arise through slow, steady evolutionary changes over time.

• Punctuated equilibrium: Long periods of little or no evolutionary change (stasis) are interrupted by short bursts of rapid change during speciation.

• Anagenesis: A single ancestral species gradually changes into a different form without branching.

• Cladogenesis: An ancestral species branches into two or more descendant species.

Explain what kinds of opportunities and conditions can give rise to adaptive radiations

• Adaptive radiations occur when organisms can exploit new ecological niches with little competition.

• They can result from colonizing new habitats, the extinction of competitors, or the emergence of key innovations that allow organisms to use new resources.

Describe factors that can drive extinction

• Habitat loss, competition, and inability to adapt to environmental changes can cause extinction.

• Small populations are especially vulnerable because they have less genetic variation, making adaptation more difficult.

Distinguish between background extinctions and mass extinctions

• Background extinction: The normal, ongoing rate of extinction over time (approximately 0.1–2 species per million species per year).

• Mass extinction: A statistically significant increase in extinction rates above the normal background rate, resulting in major biodiversity loss.

Describe two abiotic factors potentially responsible for mass extinctions

• Large-scale volcanic activity: Releases greenhouse gases, toxic metals, and gases that cause acid rain, ocean acidification, and decreased oxygen levels.

• Asteroid impacts: Can drastically change Earth's climate and environmental conditions, contributing to widespread extinction.

Explain how humans are affecting biodiversity

• Humans contribute to biodiversity loss through habitat destruction, deforestation, overfishing, introduction of invasive species, and increasing carbon dioxide emissions.

• Increased CO₂ causes global warming and ocean acidification, which threatens coral reefs, shell-bearing organisms, and other species.

Discuss whether human influence may lead to another mass extinction.

• Yes. Scientists believe a sixth mass extinction is already underway due to human activities.

• The average vertebrate extinction rate over the last 100 years is approximately 114 times higher than the background extinction rate. Climate change may make the problem worse as its effects continue to increase.