Evolution and Biodiversity Unit 1

Unit 1: Evolution and Biodiversity

• Evolution encompasses concepts like phylogenetic trees, population evolution, species origin, and the history of life
• Biodiversity includes bacteria, archaea, protists, fungi, and plants

Adaptive Radiation & Phylogeny (Ch. 25 & 26)

• Phylogenetic trees illustrate evolutionary relationships between organisms.
• Character tables summarize anatomical features for comparison and analysis across taxa.

Synopsis for today

• Review of sexual selection & species hybridization zones is necessary
• Understanding the history of life on Earth and phylogeny are essential learning objectives

Recap: Sexual Selection

• In Lake Victoria, there's a decline in species potentially from water pollution.
• A hypothesis proposes female mate choice based on male coloration.
• This nonrandom mating is a key aspect of sexual selection.
• Experiments have supported the hypothesis

Hybrid Zones Exist Between Separate Species

• Hybrid zones are geographic areas where species interbreed and produce hybrid offspring.
• Hybrid zones are often narrow along altitudinal gradients, despite individuals freely crossing the zone.
• Hybrid offspring may have developmental defects leading to low survival rates, leading to species separation.

Formation of a Hybrid Zone & Possible Outcomes

• Gene flow occurs between populations when a barrier to gene flow is removed, creating a hybrid zone.

• Possible outcomes include reinforcement, fusion, and stability of hybrid zones.

How Fast Does Speciation Occur?

• Darwin proposed that species originate through a gradual accumulation of traits over time, in contrast to a rapid "sprinting" development.

Why Aren't There More Intermediate Fossils?

• The record of intermediate fossils can be incomplete due to taphonomy.
• Speciation events can occur allopatrically (in different geographic locations) in addition to gradualism.

Punctuated Equilibrium Model

• Rapid bursts of change in species are followed by periods of relatively little change.

Scale of Geologic Time

• If Earth's history were compressed into one hour, major events would occur within minute portions of time.
• For example, animals appeared almost 9 minutes from the start of the hour, and humans appeared in the last 0.2 seconds, demonstrating a timeline of evolution.

Important Events

• Significant events like colonization by plants and arthropods, the rise of reptiles, and the diversification of mammals mark different periods.
• These events, separated by millions of years.

Continental Drift

• The movement of Earth's continents plays an important role in evolution.
• Continents are drifting apart at a rate of 2 centimeters per year.
• Plate tectonics and continental drift shape evolutionary processes.

Mass Extinctions

• Permian Extinction affected roughly 96% of marine species and terrestrial species.
• Cretaceous extinction saw dinosaurs (except birds) go extinct along with many other life forms (including ~50% of marine species).
• Causes for mass extinctions include significant volcanic eruptions, and in one specific case, perhaps an impactor from space.

Is a Sixth Mass Extinction Under Way?

• Human activity poses concerns regarding potential mass extinction events.

After Mass Extinctions Adaptive Radiation

• Mass extinctions often lead to explosive increases in diversity as surviving organisms exploit new environmental opportunities.
• The adaptive radiation of mammals post-dinosaur extinctions is an example.

What Else Can Lead to Adaptive Radiation?

• Colonization of a new environment, like the Hawaiian islands, can trigger adaptive radiation; in this case a tarweed ancestor

Over Geologic Time

• The evolution of life forms has led to a diverse range of organisms.

Biologists have Identified and Named Close to 2 Million Species

• New species are constantly identified and named.
• Current estimates are that the number of undiscovered species are in the range of 5-30 million.
• Systematics is the study of the diversity of life, aimed at organizing and categorizing these species.

Taxonomy

• Species are organized into a hierarchical classification system including domain, kingdom, phylum, class, order, family, genus, and species.

Phylogeny

• The evolutionary history of a group of organisms.
• Understanding evolutionary relationships through fossil evidence, morphological similarities, and molecular homologies.
• Evolutionary patterns, from traits to divergence, are related to lineages through time.

Do these Trees Convey the Same Information?

• Different tree orientations yield analogous information relating lineages through evolutionary time.

Primitive & Derived Characteristics

• Traits present in the ancestral group are primitive, while those unique to a lineage are derived.
• Determining ancestral and derived characteristics helps in phylogenetic analysis and classification.

If humans evolved from apes, then why are there still apes?

• Incorrect perception of evolutionary process, evolutionary pathways are like branching trees rather than linear progressions.

Summary

• Organisms diversify and extinction events or large-scale processes cause changes in evolutionary processes.

Next: Diversity of Life -- Prokaryotes

• Prokaryote lineages are a diverse and important group of organisms to study.

Monophyletic, Paraphyletic & Polyphyletic

• Definitions and examples of these ways to classify organisms grouped by relatedness
• Understanding the criteria for differentiating these groups in evolutionary trees

Paraphyletic vs polyphyletic groups

• Organisms are grouped in a way that encompasses all common ancestors of a group but not all descendents.
• Organisms may be grouped in a way encompassing multiple branches from different ancestors

Streamlined Shape

• Streamlined body shapes are analogous traits in whales, dolphins, penguins, seals, and sharks.
• Analogous traits are similar traits that developed independently, not being evolutionarily related.

This quiz covers the foundational concepts of evolution and biodiversity, including phylogenetic trees, sexual selection, and hybrid zones. Students will also explore the history of life on Earth and the adaptive radiation of various species. Prepare to demonstrate your understanding of these essential biological principles.