HOW POPULATIONS EVOLVE I DIVERSITY IS ONE OF THE

4 DIRECTION DÉPARTEMENTALE DE LA PROTECTION DES POPULATIONS SERVICE
49 PHENOTYPIC VARIATION AMONG ISLAND POPULATIONS OF A DAY
ABP1 – ALTERNATIVE BENEFIT PLAN POPULATIONS STATUTE 1937(A)(1)(A) AND

AGREEMENT ON THE CONSERVATION OF POPULATIONS OF EUROPEAN BATS
APR GICC2BIODIVERSITÉ CC ET STRATÉGIES DÉMOGRAPHIQUES DES POPULATIONS PISCICOLES
BIOSYSTEMATICS OF PSYTTALIA SPECIESPOPULATIONS (HYMENOPTERA BRACONIDAE) ATTACKING FRUIT FLIES

How Populations Evolve I


Diversity is one of the key aspects of biology

The diversity of living organisms is called biodiversity

Change is normal in biology

This makes sense since the planet is constantly changing


The Diversity of Life

For all of human history, people have named, described, and classified the inhabitants of our natural world


Taxonomy is the branch of biology concerned with identifying, naming, and classifying species


The Linnaean system includes a method of naming species and a hierarchical classification of species into broader groups of organisms

In the Linnaean system, each species is given a two-part Latinized name, a binomial

The first part of a binomial is the genus (plural, genera), a group of closely related species

The second part of a binomial is used to distinguish species within a genus


Linnaeus also introduced a system for grouping species into a hierarchy of categories

Beyond the grouping of species within genera, taxonomy extends to progressively broader categories of classification - family, orders, classes, phyla (singular, phylum), kingdoms, and domains


Grouping organisms into broader categories is a way to provide structure for our understanding of the world

However, the criteria used to define more inclusive groups such as families, orders, and classes are ultimately arbitrary


Explaining the Diversity of Life

Before the 1800s, it was thought that the earth was only about 6000 years old

All of life must have come into being relatively recently and in the current forms that were seen

However, the discoveries of fossils of creatures no longer alive confused this line of thought


Lamarck and Evolutionary Adaptations

Naturalists compared fossil forms with living species and noted patterns of similarities and differences

In the early 1800s, French naturalist Jean-Baptiste de Lamarck suggested that the best explanation for these observations is that life changes, that it evolves

Lamarck explained evolution as the refinement of traits that equip organisms to perform successfully in their environments

He proposed that by using or not using its body parts, an individual may develop certain traits that it passes on to its offspring

Of course, Lamarck was wrong in his ideas but his progressive thinking set the stage for other naturalists to follow


Charles Darwin

In 1831, Charles Darwin set sail on the H.M.S. Beagle, employed as the ship’s naturalist and captain’s companion


Darwin’s thoughts were shaped by the ideas of many of his contemporaries

Charles Lyell noted the dynamic geological nature of Earth

Jean-Baptiste de Lamark explored the possibility of descent with modification

Cuvier noted the extinction of some species Earth and the appearance of others within different time-frames


Darwin spent many years thinking about descent with modification before he concluded that the driving force was natural selection

The key piece was an essay by Thomas Malthus on the limits of human population growth


Alfred Russel Wallace

Another English naturalist, Alfred Russel Wallace also concluded that natural selection is the principal process underlying evolution


In 1859, Darwin finally published On the Origin of Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life

He pulled together ideas about:

the vast diversity of organisms

their similarities and differences

their origins and relationships

their geographical distribution

their adaptations to the surrounding environments


Descent with modification

Darwin argued that there was clear evidence that modern species are descended from earlier ancestral species

Used the term “descent with modification”, not “survival of the fittest”

He proposed that the descendants of the earliest organisms spread into various ecological habitats over millions of years

They then accumulated different modifications or adaptations appropriate to these diverse ways of life


In the Darwinian view, the history of life is like a tree

At each fork of this evolutionary tree is an ancestor common to all of the evolutionary branches that extend from that fork

There are successful (surviving) and unsuccessful (extinct) branches of the tree

Once a branch ends, there are no more descendants of that lineage

But “surviving” refers to an instant in time


Evidence of evolution

Evolution has left, and continues to leave observable signs

There is extensive evidence in the fossil record

There are also historical vestiges seen in modern life

Radiometric dating has provided accurate data for the age of the planet as well as the times of various major geological events


Fossil record

Fossils are preserved remnants or impressions left behind by organisms

Most fossils are found in sedimentary rocks

Because of this, each rock strata contains a unique set of fossils that represents a local sampling of organisms that lived when the sediment was deposited

Fossils from the same evolutionary periods are consistently found together in the same geologic strata

We have also found a consistency between the relative ages of fossils as assigned by evolutionary theory and the absolute ages determined by radiometric dating


Comparative anatomy

The comparison of body structures between different species

Similarities indicate common ancestry


Forelimbs of mammals

They have different functions

They have similar structures

Particularly the skeletal elements

The structural similarity due to common ancestry is called homology

This confirms that evolution is a constant remodeling process

Old structures are modified to provide new functions


Unfortunately, this descent with modification also leads to anatomical imperfections

Consider the human spine and knee joint

The retina of the eye is essentially installed backwards

Goose bumps attempt to warm us by fluffing up our long-gone fur


Descent with modification also leads to vestigial characters - structures which used to serve a purpose but no longer do so


Comparative embryology

The comparison of structures that are present during the early development of different organisms

Related organisms often have similar stages of embryonic development

All vertebrate embryos have a stage in which gill pouches are present

Many organisms show embryonic structures that are gone by birth


Darwin considered embryology “... the strongest single class of facts in favor of change of forms.”


Biogeography

This is the study of the geographical distribution of species, both surviving and extinct

Discoveries in the field of biogeography were crucial to the development of Darwin’s ideas


The animals and plants of the Galápagos Islands resembled species found on the South American mainland more than those found on similar but distant islands (Cape Verde Islands)


Biogeography can explain the prevalence of certain types of organisms in certain places


Australia

There are a wide variety of marsupials but relatively few placental mammals

This is much different from anywhere else in the world

Introduced placental mammals have thrived in Australia

The early Australian marsupials evolved in isolation from other regions where early placental mammals diversified

In Australia, the marsupials were just more successful


Madagascar

Lemurs are only found in Madagascar

Their closest relatives are in Africa


Biogeography can also explain the unique distribution of certain organisms

Like the lungfish

The past and current distribution of organisms indicates that life on Earth has been shaped by major geological forces over vast periods of time


Molecular biology

DNA, RNA, proteins, macromolecules

The more closely related two species are, the more similar the genes and gene products

The more distantly related, the more different the genes and gene products


Based on the degree of similarity, can determine how related two species are

Remember that the same genetic code is used for all living organisms


Evolutionary Trees

Homologous structures, both anatomical and molecular, can be used to determine the branching sequence of an evolutionary tree

Some homologous characters, such as the genetic code, are shared by all species because they date to the deep ancestral past

In contrast, traits that evolved more recently are shared by smaller groups of organisms


CHAPTER 15 TEMPORAL AND SPATIAL DYNAMICS OF POPULATIONS CHAPTER
CHRISTIANMUSLIM CONFLICT IN ETHIOPIA MUSLIM AND CHRISTIAN (ORTHODOX) POPULATIONS
CHUTES AND LADDERS FOR DIVERSE POPULATIONS TOTAL TIME 45


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