Taught by Anthony Martin, John Hawks
This course is intended as an overview of significant evolutionary
transitions in the 4.0 billion - year history of life. The first lecture
introduces students to basic concepts of macroevolution, including the
factors responsible for significant changes in life over the course of
geologic time: geographic isolation, genetic drift, environmental change,
and natural selection. One of the best ways to study evolutionary
transitions is through paleontology (the study of ancient life and
fossils), the topic of Lecture 2. The second lecture also covers major
eras and periods of the geologic time scale and explains how radiometric
age dating confirms the ages of rocks and fossils.
Lecture 3 discusses the evolution of one - celled organisms, delving
into the two major types of cells (prokaryotes and eukaryotes) and their
differences. Knowing these distinctions, we explore the likely role of
symbiosis in the evolution of prokaryotes into eukaryotes and examine the
fossil evidence for one - celled organisms from about 3.5 to 1.5 billion
years ago. Lecture 4 reviews the early evolution of multicellular animals
(metazoans), the fossils of which are represented worldwide in rocks from
about 600 to 550 million years ago. Lecture 5 is about the Cambrian period
(545 to 505 million years ago) and the next significant transition in the
evolution of animals: the formation of mineralized skeletons. Skeletons
were probable evolutionary responses to predation but are also linked to
the changing chemistry of the Cambrian ocean and atmosphere. Lecture 6
explores the evolution of some Cambrian invertebrate animals into animals
with primitive .backbones. and other anatomical innovations, leading to
the first chordates and vertebrates.
In Lecture 7, we review the evolutionary challenges faced by algae,
fungi, plants, and animals that adapted to terrestrial environments
during the early part of the Paleozoic era (about 500 to 350 million years
ago). Connected to this topic is the early evolution of insects, the most
successful group of animals today. In Lecture 8, we look at insect origins
from the fossil record of the Devonian period (410 to 360 million years
ago) and examine evidence that some insects evolved into the first known
flying animals during the Carboniferous period (360 to 285 million years
ago). The evolution of seed plants in the Devonian period resulted in the
first true forests, the subject of Lecture 9. Also during the Devonian
period, four - limbed vertebrates (tetrapods) evolved from lobe - finned
fish. In Lecture 10, we learn about the fossil evidence for this transition,
the anatomy of lobe - finned fish and amphibians, and the reflections of
their traits in all tetrapods, including humans. Later, in the Carboniferous
period, egg - laying reptiles evolved from amphibians, which allowed
tetrapods to live in dry - land environments; this topic is discussed
in Lecture 11.
Lecture 12 deals with the early evolution of dinosaurs from ancestors shared
by modern crocodilians and flying reptiles (pterosaurs), before they evolved
into the largest land - dwelling carnivores and herbivores of all time.
In Lecture 13, we study the origins and diversification of a wide variety of
reptiles that swam in the seas and flew through the air during the Mesozoic
era (250 to 65 million years ago), including mosasaurs, plesiosaurs,
icthyosaurs, and pterosaurs. Lecture 14 deals with birds, which evolved from
theropod dinosaurs during the Jurassic and Cretaceous periods (about 150 to
65 million years ago). Hence, this lecture emphasizes the evolution of
feathers and flight in dinosaurs that proliferated into the diversity of birds
seen today. On land during the Cretaceous period (145 to 65 million years ago),
a major transition between non - flowering and flowering plants took place that
resulted in the coevolution of their pollinators. Lecture 15 takes us back to
the first primitive flowering plants, while also considering how pollinating
animals (especially insects) must have evolved along with the bearers of fruit.
Lecture 16 covers the reptiles of the Permian period (285 to 250 million years
ago) that evolved mammalian traits, as well as the fossil record for the arrival
of the first true mammals, about 225 million years ago (in the Triassic period).
This lecture also offers an overview of the major mammal groups.
The mass extinction that ended the Cretaceous period 65 million years ago opened
many niches for surviving species of plants and animals, including mammals. Among
the evolutionary transitions that took place about 50 million years ago was that
of land - dwelling hoofed mammals to marine environments, which led to the
evolution of modern whales. Lecture 17 explores the fossil evidence for this
transition, highlighting anatomical features that connect these massive animals
with their smaller terrestrial ancestors. Just before this time, many kinds of
mammals took to the trees, developing adaptations to newly evolved fruits, flowers,
and leaves. These developments resulted in the first primates about 60 million years
ago, the topic of Lecture 18. By about 45 million years ago, some of these primates
evolved into the ancestors of today's monkeys and apes. Lecture 19 describes these
primates, their adaptability, probable social habits, and dispersal to new habitats.
Lecture 20 deals with the evolution of some ape lineages from 12 to 7 million years
ago, some of which began to walk upright, and describes their different sizes, diets,
and lifestyles.
The evolutionary path to humanity is the subject of Lecture 21, in which we review
the first stone tools, from 2.6 million years ago, marking a change to a human -
like social and cognitive system characterized by hunting and gathering. Soon, the
descendants of these toolmakers spread more widely than earlier hominids. Lecture
22 looks at how modern humans, once evolved, began to cross Africa about 100,000
years ago, dispersing into Europe and Asia and challenging Neandertals, which are
now described by the Neandertal genome. Lecture 23 covers rapid changes in modern
human genes, spurred by our high - density agricultural lifestyle and epidemic
diseases, as well as human impacts on the Earth's ecology. With this perspective
in mind, Lecture 24 summarizes the common themes of major evolutionary transitions,
while providing a few examples of how fossils, artifacts, and other evidence help
us to better understand the history of life.
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