ZOOHCC - 602: Evolutionary Biology (Theory) Unit:-1
Geological time scale
The Geological Time Scale is a system of chronological dating that divides
the Earth's history into distinct periods of time based on the study of rock
layers and the fossils found within them. It is divided into four major
divisions: Eons, Eras, Periods, and Epochs.
The largest division of time is the Eon, which is further divided into
Eras. The Phanerozoic Eon, for example, is divided into three Eras:
Paleozoic, Mesozoic, and Cenozoic.
Each Era is divided into Periods. For example, the Paleozoic Era is divided
into six periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous,
and Permian.
Each Period is further divided into Epochs, which are the smallest
divisions of time in the Geological Time Scale.
The Geological Time Scale allows scientists to understand the history of
the Earth and the evolution of life on it. It also helps geologists and
other scientists to date rocks and fossils accurately and to correlate them
with other rocks and fossils from around the world.
The diversity of animal life on Earth has changed over time, with different
groups of animals evolving and going extinct throughout Earth's history.
Here are some examples of animals found in each of the major periods of the
geologic time scale:
Cambrian Period:-
The Cambrian is known as the "explosion of life" because it saw the rapid
diversification of many major animal groups. Some of the animals that
evolved during this time include trilobites, brachiopods, echinoderms, and
arthropods.
Ordovician Period:-
The Ordovician saw the continuation of many Cambrian animal groups, as well
as the evolution of new ones. Some of the animals that evolved during this
time include cephalopods, bryozoans, graptolites, and jawless fish.
Silurian Period:-
The Silurian saw the diversification of many marine animal groups,
including the first appearance of jawed fish. Some of the animals that
evolved during this time include early corals, gastropods, ammonites, and
early sharks.
Devonian Period:-
The Devonian saw the emergence of many new animal groups, including the
first land animals. Some of the animals that evolved during this time
include amphibians, insects, early tetrapods, and placoderms.
Carboniferous Period:-
The Carboniferous saw the emergence of many new terrestrial animal groups,
including the first reptiles. Some of the animals that evolved during this
time include reptiles, synapsids (early mammal relatives), and insects such
as dragonflies and cockroaches.
Permian Period:-
The Permian saw the diversification of many reptile and mammal-like groups,
as well as the emergence of some early mammal groups. Some of the animals
that evolved during this time include therapsids (early mammal relatives),
archosaurs (early dinosaurs), and early turtles.
Mesozoic Era:-
The Mesozoic era saw the dominance of the dinosaurs and the emergence of
many modern animal groups. Some of the animals that evolved during this time
include birds, mammals, pterosaurs, and marine reptiles such as ichthyosaurs
and plesiosaurs.
Cenozoic Era:-
The Cenozoic era saw the diversification and dominance of many modern
animal groups, including primates, ungulates, carnivores, and rodents. Some
of the animals that evolved during this time include humans, whales, horses,
and elephants.
Dominant plants and animals in each of the major periods
Here are some examples of dominant plants and animals in each of the major
periods of the geologic time scale:
Paleozoic Era:
Devonian Period: A dominant plant during this time was Archaeopteris, an
early tree that grew up to 30 meters tall. A dominant animal was
Dunkleosteus, a large armored fish that lived in the shallow seas.
Mesozoic Era:
Jurassic Period: A dominant plant during this time was Cycadeoids, a group
of plants related to modern cycads. A dominant animal was Stegosaurus, a
large herbivorous dinosaur known for its distinctive bony plates along its
back.
Cretaceous Period:-
A dominant plant during this time was the angiosperms, or flowering plants,
which rapidly diversified during this period. A dominant animal was
Tyrannosaurus rex, a large carnivorous dinosaur that is one of the most
famous dinosaurs in history.
Cenozoic Era:-
Paleogene Period: A dominant plant during this time was the palm tree,
which grew in tropical and subtropical regions. A dominant animal was
Ambulocetus, an early whale ancestor that lived both on land and in
water.
Neogene Period:-
A dominant plant during this time was the grasses, which began to spread
and diversify during this period. A dominant animal was Megatherium, a giant
ground sloth that lived in South America.
Quaternary Period:-
A dominant plant during this time was grasses, which continued to spread
and diversify. A dominant animal is Homo sapiens, or modern humans, who have
had a major impact on the planet's ecosystems and have become the most
dominant species on Earth.
Specifically
Paleozoic Era:
Devonian Period:
A dominant plant during this time was Archaeopteris, an early tree
that grew up to 30 meters tall. A dominant animal was Dunkleosteus, a large
armored fish that lived in the shallow seas.
Mesozoic Era:
Jurassic Period:
A dominant plant during this time was Cycadeoids, a group of plants related
to modern cycads. A dominant animal was Stegosaurus, a large herbivorous
dinosaur known for its distinctive bony plates along its back.
Cretaceous Period:
A dominant plant during this time was the angiosperms, or flowering plants,
which rapidly diversified during this period. A dominant animal was
Tyrannosaurus rex, a large carnivorous dinosaur that is one of the most
famous dinosaurs in history.
Cenozoic Era:
Paleogene Period:
A dominant plant during this time was the palm tree, which grew in tropical
and subtropical regions. A dominant animal was Ambulocetus, an early whale
ancestor that lived both on land and in water.
Neogene Period:
A dominant plant during this time was the grasses, which began to spread
and diversify during this period. A dominant animal was Megatherium, a giant
ground sloth that lived in South America.
Quaternary Period:
A dominant plant during this time was grasses, which continued to spread
and diversify. A dominant animal is Homo sapiens, or modern humans, who have
had a major impact on the planet's ecosystems and have become the most
dominant species on Earth.