Chapter 25, Macroevolution

macroevolution

macroevolution descibes the evolution of species over long peiods of time

eg mass exiticntion of dinosaurs some 65mya

four main stages of life

1. The abiotic (nonliving) synthesis of small organic mol- ecules, such as amino acids and nitrogenous bases

2. The joining of these small molecules into macromol- ecules, such as proteins and nucleic acids

3. The packaging of these molecules into protocells, droplets with membranes that maintained an internal chem- istry different from that of their surroundings

4. The origin of self-replicating molecules that eventually made inheritance possible

hydrothermal vents

areas on the seafloor where heated water and minerals gush from Earth’s interior
into the ocean.

hypotheiss for how organic molecules were produced

alkaline vents

most porbale place where life orginated

other deep-sea vents that release water that has a high pH (9–11) and is warm (40–90°C) rather than hot, an environment that may have been more suitable for the origin of life

Conditions on early Earth made the origin of life possible

• Experiments simulating possible early atmospheres have pro- duced organic molecules from inorganic precursors. Amino acids, lipids, sugars, and nitrogenous bases have also been found in meteorites.

• Amino acids and RNA nucleotides polymerize when dripped onto hot sand, clay, or rock. Organic compounds can spontaneously assemble into protocells, membrane-bounded droplets that have some properties of cells.

• The first genetic material may have self-replicating, catalytic RNA. Early protocells containing such RNA would have increased through natural selection.

fossils records

The fossil record, based largely on fossils found in sedimentary rocks, documents the rise and fall of different groups of organ- isms over time

• The fossil record shows how new groups of organisms can arise via the gradual modification of preexisting organisms.

usually sedimentary rock

requires rapid burual in an oxygen poor environment

sedimentary strata

Sedimentary strata are distinct, visible layers of rock or sediment formed by the accumulation, compaction, and cementation of mineral particles over time

reveal the relative ages of fossils. The ages of fossils can be estimated by radiometric dating and other methods.

radiometric dating

a technique used to date materials like rocks or organic remains by comparing the amount of a radioactive isotope to its stable decay product

Key events in life’s history

include the origins of unicellular and multicellular organisms and the colonization of land

unicellular organisms

a living thing that is made of only one cell either:

• Prokaryotes: Cells that do not have a true nucleus or membrane-bound parts. Bacteria are the most common example.

• Eukaryotes: Cells that have a clear nucleus holding their DNA and other specialized parts. Examples include amoebas and yeas

multicellular organisms

a living thing that is made up of more than one cell and has different cell types

moving of plate tectonics effect on speciation and extinction rates

continental plates move gradually over time, altering the physical geography and climate of Earth, leading to extinctions in some groups and speciation in others.

drive speciation (Increasing Diversity)by physically separating populations into isolated environments, while continental collisions increase extinction rates through heightened competition and habitat loss (decreasing diversity)

evolutionary histroy of mass extinctions

Evolutionary history has been punctuated by five mass extinctions that radically altered life’s history. Possible causes for these extinctions include continental drift, volcanic activity, and impacts from asteroids.

• They provide oppotunities for remaining species to diversify and occupy new niches.

adaptive radiations

an evolutionary process where a single ancestral species rapidly diversifies into a multitude of new forms to exploit different ecological niches

• causes diversification

• produces a group of closely related but distinct evolutionay lineages

occurs when:

• major evolutionary innovations

• that colonized new reegions in which there was little competition from other organisms

eg, The diversification of mammals following the extinction of dinosaurs

Major changes in body form

result from changes in the sequences and regulation of developmental genes

developmental genes

Developmental genes affect morphological differences between species by influencing the rate, timing, and spatial patterns of change in an organism’s form as it develops into an adult.

what causes evolutionary trends

natural selection in a changing environment or species selection, resulting from interactions between organisms and their current environments.

• It creates selective pressures that favor cetain traits over others.

horizontal gene transfer

the movement of genetic material between organisms by any mechanism other than vertical transmission from parent to offspring

• trasnformation

• transduction

• conjuction

the prokaryotic way of generating genetic diversity

How does supercoiling work for circular DNA?

By over-winding or under-winding the double helix, which forces the circular molecule to twist around itself in 3D space like a tangled phone cord to relieve the mechanical strain

Negative supercoiling

The DNA helix is untwisted relative to its relaxed state. This stores energy that makes it easier for the two strands to separate, which is why most natural cellular DNA is negatively supercoiled to assist with replication and transcription

Positive supercoiling

The DNA helix is tightly twisted beyond its normal state. This makes strand separation much harder, though it helps protect the DNA of extreme heat-loving organisms (thermophiles) from melting apart.

Reverse Gyrase

 It is the only known enzyme that actively wraps DNA into a right-handed, positive supercoil, which protects genetic material from melting at extreme heat. Thus, evidence that LUCA occurred at high heat. 

betrwayed LUCA as she lived in hot water, a thermophile

what si serpetenization and what ions are primarily formed

the result of the interaction of ocean water with rocks of the Eath cust.

CH4, OH-, and H2

Which molecules or ions were used by the C-fixation pathway of LUCA?

CO2 and H2

For terestial animals and plants, the most recent mass extinction event that occured pior to the evolution of humans took place when

65 millino years ago

The most severe mass extinction was

Pemian extinction, 250 mya

what is the main process behind the appearance of new species in phyletic gradualism?

Anagenesis

Phyletic gradualism is an evolutionary model stating that new species arise from the slow, steady, and continuous transformation of ancestral populations over long period

What is the difference between micro- and macroevolution?

Microevolution descibes the evolution of organisms in populations, while macroevolution descibes the evolution of species over long peiods of time.

Which gas was present only in negligible concentrations duing the pre-biotic peiod atmospere in the Hadaean aeon?

O2

non disjunction

Nondisjunction is the failure of paired chromosomes to separate properly during cell division, leading to cells with an abnormal number of chromosomes

Which era is characteized by the dramatic diversification of the eukayotes?

Cambrian

Absence of oxygen in eath, made the atmosphere reducing. But it later became oxidizing in nature due to the emergence of

Cyanobacte

what are Fossilized stromatolites

resemble stuctures fomed by bacteial communities that are found today in some wam, shallow, salty bays.

Adaptive radiations can be a direct consequence of what three factors

evolutionay innovation

vacant ecological niches

colonization of an isolated region that contains suitable habitat and few competitor species

Which event is pimaily associated with the Phanerozoic eon?

The evolution of most animal species

What distinguishes eukayotic cells from prokayotic cells?

They have membrane-bound organelles, including a nucleus.

The oxygen revolution enabled the development of what, what porcess contributed to thsi revolution, and what caused the oxygen revolution?

• Aerobic metabolism

• photosynthesis by cyanobacteia

• The accumulation of oxygen in the atmosphere due to photosynthesis

What advantage did multicellulaity offer to early organisms?

Cell specialization and the development of complex body stuctures

When did the Hadean eon begin and what was isgnfincance

4.6 billion years ago, establishing Earth's core, crust, magnetic field, and early ocean

Proterozoic eon

The transition from single-celled to multicellular organisms, eukaryotes

2.5 billion years ago

Which molecule is hypothesized to have been the first to store genetic infomation and catalyze reactions in early life foms?

RNA

which factor is believed to have contibuted to the Late Devonian extinction, pimaily affecting maine life

The spread of plants that altered soil and water chemisty

Fossils from which eon provide evidence of the earliest known foms of life?

Archean eon

4 billion years ago

How can changes in the regulation of developmental genes impact evolution?

They can lead to major differences in body fom by changing how genes are tuned on or off duing development.

Which of the following was a cucial adaptation that led to multicellulaity?

Cell-to-cell communication and cooperation

The Pemian-Tiassic mass extinction, often called "The Great Dying," is believed to have been caused by which event?

Massive volcanic euptions in Sibeia, causing severe global waming and ocean acidification

What is paedomorphosis?

The early maturation of reproductive traits while maintaining juvenile body stuctures

Multicellular organisms first appeared approximately how many years ago?

1.2 billion

Why was the oxygen revolution citical for the development of complex life?

It provided the atmospheic oxygen necessay for aerobic respiration

The earliest foms of life on Eath are thought to be

Single-celled prokayotes

How do differences in speciation and extinction rates affect groups of organisms?

They detemine which groups dominate ecosystems at different times.

heterochrony and How does heterochrony affect evolutionay changes?

an evolutionary change in the timing or rate of developmental events in an organism compared to its ancestors

It influences the shape and size of vaious body stuctures by modifying the growth rates of different pats of the organism.

Prokayotes first appeared approximately how many years ago?

3.5 billion

What is believed to have caused the mass extinction at the end of the Cretaceous peiod?

A large asteroid impact, leading to climate changes

145 million years ago

Why was the colonization of land by plants and fungi significant in Eath’s histoy?

It increased biodiversity and paved the way for animal life on land.

Which characteistic was essential for the suvival of early animals on land?

The development of lungs

In the context of early Eath, which process has long been hypothesized to be cucial for the fomation of macromolecules like proteins?

The spontaneous assembly of amino acids into polymers on hot sufaces or clay

What are prokayotes?

Single-celled organisms lacking a nucleus and membrane-bound organelles

why are Protocells impotant in early evolution

Provided a segregated environment where biochemical reactions could occur

their ability to miantian an internal environment diferent from their surroundings curical for development fo early life

Hox Gene

impotant in detemining the body plan of an organism duing development

How can new morphological foms aise from changes in gene sequences?

Through mutations in the regulatoy elements of developmental genes, leading to new expressions of physical traits

. Eukayotic cells first appeared approximately how many years ago?

1.8 billino

Which of the following was most likely absent from the early processes that led to the fomation of macromolecules?

Enzymes to facilitate the fomation of polymers

What likely caused the Ordovician-Siluian mass extinction, which wiped out around 85% of maine species?

A volcanic euption that released toxic gases

What effect did the oxygen revolution have on prokayotic life?

It caused a mass extinction of oxygen-sensitive organisms.

What adaptation allowed early plants to suvive on land?

The presence of a vascular system

What is the role of gene duplication in the evolution of new traits?

Gene duplication creates additional copies of genes that can acquire new functions over time.

Which group of organisms is considered among the earliest multicellular life foms?

Algae

What contibuted to the abiotic synthesis of organic molecules on early Eath?

Reducing conditions and energy sources like lightning

How did early prokayotes obtain energy?

Through chemosynthesis

The RNA world hypothesis suggests that:

RNA molecules could have seved both as genetic mateial and as catalysts

Which major evolutionay change is associated with the transition from unicellular to multicellular life?

the specialization of cells into tissues and organs

Which organisms were the first to colonize land?

Fungi and plants

Tetrapods were among the first animals to colonize land. Which group do they belong to?

vertebrates