Biology 100 Unit 15 Flashcards
Earth is considered _________________
4.6 billion years old
3 things about Prokaryotes
–evolved by 3.5 million years ago
– Began oxygen production about 2.7 billion
years ago
– Lived alone for almost 2 billion years
Single-celled ________________________ are considered to have evolved about 2.1 billion years ago.
eukaryotes
_____________________ are considered to have evolved approximately 1.2 billion years ago.
Multicellular eukaryotes
is stored geological layers
Biological history
2.5 billion year-old fossilized prokaryote mats suggest that photosynthetic bacteria produced
O2 , which created an aerobic atmosphere important for life.
These fossilized mats containing photosynthetic bacteria are called _________________.
stromatalites
This is referred to as the __________ _____________.
oxogen revolution
Earth’s early atmosphere probably contained
H2O, CO, CO2, N2, and possibly some CH4.
Theabsenceof oxidation in the oldest rocks shows that there little or no ____________was present.
O2
In the ancient world
Volcanic activity, lightning, and UV radiation were likely prevalent
All organisms today arise via ______________ stating that life comes from life, however how did the 1st living organisms get here?
biogenesis,
This discrepancy is known as the ______________, still no complete answer to this dilemma
biogenesis
According to current hypotheses, the first organisms arose via chemical evolution in 3 stages.
– 1. Collection of monomers
– 2. Formation of RNA polymers (simple genes)
– 3. Assembly of complementary RNA (replication)
were likely synthesized from simpler molecules…this takes energy
Macromolecules
On the early Earth, it is proposed that inorganic chemicals were energized by
lightning or UV radiation and combined to form new structures.
In 1953, ______________ simulated what he thought was the “early earth” in his laboratory.
stanly miller
Simple organic molecules can polymerize on hot rocks or clay.esent on the early earth.
– This can produce polypeptides and short nucleic acids. – Short RNA pieces may have been acted as the 1st type
of nucleic acid pr
in various situations does occur, however they are also often broken down into monomers during these same processes.
Polymerization of organic monomers
If a RNA polymer formed, the catalytic ability of RNA may have lead to ________________________.
self replication of RNA
- Collection of monomers
- Formation of short RNA polymers: simple “genes”
- Assembly of a complementary RNA chain, the first step in the replication of the original “gene”
Spontaneous RNA assembly
can act as rough templates for the formation of short polypeptides.
short RNA molecules
Such assemblies may act as primitive molecular co- operation
Co-ops
can then assist with RNA replication.
polypeptides
_______________are RNA molecules that act like enzymes
Ribosomes
if they are placed into an aqueous (water-based) solution, they form a self-sealing sphere
Because phospholipids have hydrophobic tail and hydrophillic heads
These membrane enveloped protecting nucleic acids an proteins had a
selective advantage
A protected chemical environment may have given rise to a primitive metabolism.
—Natural selection then favors those co-ops that are most efficient, and effectively reproduce (or divide).
– Under continued selective pressure, these may have evolved into the first simple prokaryotic cells.
All of these steps would have to have occurred ________________ in nature.
in sequence
Although scientists have not made life, they attest that over the course of billions of years, the correct combinations of macromolecules came together to form an a simple cell, _________________________ ___________________________________________
then enviromental pressures are responsible the variety we see today
are used to categorize organisms into time frames when they evolved and existed on earth
Distinct Geological eras
Radiometric dating uses _______________________ which decay with a predictable half-life. The 1⁄2 life is measured, and compared to current standards to determine the age of ancient fossils and geologic rocks.
radioactive isotopes
according to the theory of __________________________:
the Earth’s crust is divided into giant, irregularly
shaped plates that
essentially float on the underlying mantle.
plate tectonics
In a process called _______________________ that movements in the mantle cause the plates to move.
continental drift
Since the origin of multicellular life roughly 1.5 billion years ago, there have been three occasions in which the landmasses of Earth came together to form a supercontinent called
pangea
Fossils of lungfishes are found on every continent
except Antarctica.
Continental drift explains the distribution of lungfishes.
Today, living lungfishes are found in
South America, – Africa, and
– Australia.
When did lung fish evolve
when pangea was extinct
result from the movements of crustal plates.
volcanoes and earthquakes
The boundaries of plates are hotspots of
volcanoes and earthquakes
The fossil record shows that the vast majority of
species that have ever lived are now extinct.
Extinction is inevitable in a changing world.
Over the last 500 million years,
– five mass extinctions have occurred, and
– in each event, more than 50% of the Earth’s
species went extinct.
– The boundaries of plates are hotspots of volcanic and earthquake activity.
– occurred about 251 million years ago,
– defines the boundary between the Paleozoic and Mesozoic eras,
-claimed 96% of animal species
– took a tremendous toll on terrestrial life, and
– was likely caused by enormous volcanic eruptions.
The Permian mass extinction
caused the extinction of all the dinosaurs except birds
and
The Cretaceous mass extinction
The Cretaceous mass extinction
was likely caused by a large asteroid that struck the Earth, blocking light and disrupting the global climate.
are periods of evolutionary change that
adaptive radiations
adaptive radiations cause
– occur when many new species evolve from a common
ancestor that colonizes a new, unexploited area and
– often follow extinction events.
Radiations may result from the evolution of new adaptations such as
– wings in pterosaurs, birds, bats, and insects and
– adaptations for life on land in plants, insects, and tetrapods.
The fossil record can tell us
– what the great events in the history of life have been
and
– when they occurred.
provide a big-picture view of how those changes came about.
Continental drift, mass extinctions, and adaptive radiation
We are now increasingly able to understand the basic biological mechanisms that underlie the changes seen
the fossil record
– addresses the interface of evolutionary biology and
developmental biology and
– examines how slight genetic changes can produce major morphological differences.
the field of evo-devo
Genes that program development control the
- rate
- timing
- spatial pattern of change in an organism’s form as it developes
Many dramatic evolutionary transformations are the result of a change
in the rate or timing of developmental events.
is the retention in the adult of body structures that were
juvenile features in an ancestral species and
paedomormphesis
paedomormphesis occurs in the
salamander in which sexually mature adults retain gills and other larval features.
Slight changes in the relative growth of different body parts can change
an adult form substantially.
Skulls of humans and chimpanzees are
–more similar as fetuses but
– quite different as adults due to different rates of growth.
– are called master control genes and
– determine basic features, such as where pairs of wings or legs develop on a fruit fly.
homeotic genes
Profound alterations in body form can result from
– changes in homeotic genes or
– how or where homeotic genes are expressed.
Duplications of homeotic gene clusters may explain the evolution of
vertebrates from invertebrates.
we see today, may have evolved by increments from simpler versions of the same basic genes.
complex structures
In the evolution of an eye or any other complex structure, behavior, or biochemical pathway, each step must
– bring a selective advantage to the organism possessing it and
– increase the organism’s fitness.
In other cases, evolutionary novelties result from the
gradual adaptation of existing structures to new functions.
Such structures that evolve in one context but become co-opted for another function are often called ____________________.
exaptations
Examples of exaptations include
– feathers that may have first functioned for insulation
and later were co-opted for flight and
– flippers of penguins that first functioned for flight and were co-opted for underwater swimming.
Phylogeny is the
evolutionary history of a species or group of species
Phylogeny can be inferred from
– the fossil record,
– morphological homologies, and – molecular homologies.
is a discipline of biology that focuses on
Systematics
Two examples of systematics
- Classifying organisms
- Determining their evolutionary relationship
Carolus Linnaeus introduced _________________________ a system of naming and classifying species.
taxonomy,
Biologists assign each species a two-part scientific name, or binomial, consisting of
– a genus and
– a unique part for each species within the genus.
_____________are grouped into progressively larger
categories.
genera;
Each taxonomic unit is called a
taxon
the order of taxonomies
domain kingdom Phylum class order family genus species
Biologists traditionally use ____________________ to depict hypotheses about the evolutionary history of species.
phylogenetic trees
reflect the hierarchical classification of groups nested within more inclusive groups.
branching diagrams
Phylogenetic trees indicate the probable
evolutionary relationships among groups and patterns of descent.
