Diversification of Life- Unit 4

Bio 150

Macroevolution (69)

happens as populations change through evolutionary mechanisms over many millions of years, leading to speciation & extinction

Fossils (69)

the remains, impressions, or traces of a dead organism as a mold or cast in rock

Fossil record (69)

all fossils that have been found on Earth and described in the scientific literature

• is based toward certain lineages

  • contains <5% of species that have lived on Earth and some groups of species are overrepresented

• sedimentation is crucial for fossilization, introducing a habitat bias

• organism with bony or other hard structures are more likely to fossilize

  • fossils are likely to become damaged over time, resulting in bias to newer fossils

• common species are more likely to fossilize than rare species

  • abundant in numbers

  • present over a long period of time

Evidence that species change through (69)

1. vastness of geologic time

   • Radioactive decay dates the Earth at 4.6 billion years old

     • different radioactive elements have different rates of decay, allowing researchers to date rocks and fossils

   • earliest signs of life appear in rocks formed 3.4-3.8 billion years ago

   • Geological time scale: a sequence of named intervals that represent the major events of Earth’s history

2. Species have gone extinct over time

   • extinct species: a species that is no longer present on Earth

   • extant species: a species living today

   • 99% of all species that have ever lived are now extinct

   • species have gone extinct in catastrophic events and at a background rate throughout Earth’s history

3. Transitional features link older and younger species

   • a trait in a fossil species that is intermediate between ancestral and derived species (evolved from species)

4. Vestigial traits demonstrate that species evolve from ancestors

5. Species are observed changing today

Evidence that species are related by common ancestry (69)

1. related species share homologies- similarity due to common ancestry

2. similar species are found in the same geographic area

3. observations of speciation occurring in modern times

Precambrian (70)

interval between the formation of Earth 4.6 billion years ago and the appearance of most animal groups about 541 million years ago

• makes up approximately 90% of Earth’s history

Hadean Eon (70)

• first oceans; heavy bombardment (collisions with large asteroids and other bodies) from space ends

• liquid water on Earth

• Earth formation complete

• moon forms

• formation of solar system

Archaean Eon (70)

• first cyanobacteria fossils (first organisms to preform oxygenic photosynthesis)

• first evidence of oxygenic photosynthesis

• first evidence of photosynthetic cells

• origin of life

Proterozoic Eon (70)

• first eukaryotes in the fossil record- 2.2-1.7 billion years ago (first photosynthetic eukaryotes)

Key developments of the Precambrian (70)

1. liquid water

2. life- prokaryotic organisms first

3. photosynthesis

4. oxygenated atmosphere

5. eukaryotic organisms

6. multicellular life

• life was exclusively unicellular for most of Earth’s history- almost all life forms were unicellular for almost 3 billion years ago (first multicellular organisms evolved around 1.6 billion years ago)

Phanerozoic Eon (70)

makes up approximately 10% of Earth’s history

• began 541 million years ago with evolution of bilateral animals

• shortest eon but has shown greater diversity than the Precambrian combined

adaptive radiation (70)

occurs when a single lineage rapidly produces many descendant species with a wide range of adaptive forms

• new innovations in traits or behaviors

• new niche space

Cambrian explosion (70)

rapid diversification of animals during the Cambrian period (aquatic)

Devonian plant explosion (70)

rapid diversification of land plants during the Devonian period (terrestrial)

Bacteria and archaea are prokaryotes (72)

• cell lacks a membrane bound nucleus and most organelles

• all cells (prokaryotic & eukaryotic) have genetic material, a plasma membrane and ribosomes

• all bacteria and archaea are unicellular-organisms consist of one cell

Plants, animals, fungi, and protists are eukaryotes (72)

• eukaryotic organisms have cells with membrane-bound nuclei as well as many organelles

  • can be single or multicellular

• most eukaryotic organisms are protists

Bacteria and archaea are prokaryotic microbes (73)

• lineages are ancient, diverse, abundant, and ubiquitous

• in terms of total volume, bacteria and archaea are the dominant life forms on Earth today

Microbe- microscopic organisms

Microbiome (73)

the community of microbes that naturally inhabits a particular area

Extremophiles (73)

bacteria and archaea that live in high-salt, high-temperature, low-temperature, or high-pressure habitats (found almost everywhere)

Hot area of research because:

1. helps understand the origin of life

2. explorations in extraterrestrial life

3. commercial applications: enzymes that function at extreme temperatures

Autotrophs (73)

generate their own energy

Photoautotrophs (73)

generate energy from sunlight through photosynthesis

• photosynthesis has not been reported in archaea

Chemoautotrophs (73)

generate energy from organic or inorganic chemical compounds

• both bacteria and archaea

Heterotrophs (73)

gain energy from molecules produced by other organisms

Many heterotrophic prokaryotes are symbiotic (73)

• mutualists such as nitrogen fixing bacteria or beneficial bacteria in the gut microbiome

• parasitic, such as bacteria in the gut microbiome that feed on energy sources

Key differences between bacteria and archaea (74)

1. bacteria have a peptidoglycan in the cell wall

2. machinery used in the central dogma in archaea are more like those found in eukaryotes than bacteria

Pathogens (74)

microorganisms that cause disease

Virulence (74)

the degree to which a pathogen causes diseases in its host

• is a heritable trait

• is often tied to the role of replication of bacteria

Antibiotics (74)

kill bacteria or stop them from growing

• are produced naturally by a wide array of soil-dwelling bacteria and fungi- hypothesized to reduce competition

• usually target the cell walls of bacteria