The Origin of New Species · • Adaptive radiation is divergent evolution that has resulted in the formation of, at the very least, new ... and reptiles (swimming dinosaurs with

The Origin of New Species

• If microevolution is small changes in gene frequencies…

• What, then would macroevolution be?

• And how might that work????

Introduction

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• In 1942 Ernst Mayr defined species.

• Can mate and have fertile offspring.

• Examples???

• Same # of chromosomes and the same sequences of

genes on them.

The biological species concept emphasizes

reproductive isolation


• Species are based on infertility, not physical similarity.

• For example, these two meadowlarks are different species.

• But all these folks belong to the same species..

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 24.2

• There are two key ingredients to the process of

speciation:

• Reproductive isolation

• A vacant niche.

• Then, time to Evolve (by what mechanisms???).

2.How can a new species come about?


• Reproductive

isolation can

occur for

many reasons.

• But very often

it is

geography.


Fig. 24.5

• Islands are great examples.

• How about those Grand Canyon squirrels?

• And marsupials

• https://www.youtube.com/watch?v=NneMKuemRmI 2:00

1. Geographic barriers can lead to isolation

and the origin of new species:


https://www.youtube.com/watch?v=NneMKuemRmI

• They also require the means to

survive - a niche they can fill.

• Gause’s Law, or the Law of

Competitive Exclusion:

• “this town’s not big enough for

the both of us.”

• The less well adapted population

will either…?Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

So here’s how it works:

• The isolated populations face different selection pressures and have different random mutations occur. Chance may also be involved

• The result is that their gene pools gradually grow different enough and, voila, they are two different species.

• Even if reunited, their members can no longer mate and produce fertile offspring.

Common ancestor???

adaptive radiation???

divergent evolution ???


Fig. 24.11

Items referring to adaptive radiation, convergent evolution, coevolution, or punctuated equilibrium should focus on the concepts rather than on the definition of the terms.

Divergent Evolution

• This is the main pattern we see when we look at the history of life on earth.

• It is the branching tree pattern of a common ancestor giving rise to different species, orders, kingdoms, etc.

• Similarities in homologous structures, chemicals like DNA and embryological development all are evidence of evolutionary change with this pattern.

• Adaptive radiation is divergent evolution that has resulted in the formation of, at the very least, new species. The two terms are almost synonyms.


Fig. 24.24

• Convergent Evolution, on the other hand is a pattern we see in which groups which, even though they diverged from a common ancestor in the past, were different from each other at one point in time and then later evolved analagous structureswhich serve similar functions.

• Two classic examples:

• The evolution of a streamlined body shape and fins in sharks (fishes), whales (mammals with dog-like ancestors) and reptiles (swimming dinosaurs with 4-legged, land-living ancestors).

• The evolution of wings in birds, bats and insects, all from ancestors without wings.


Now, just to be confusing, let’s look at

co-evolution.

• This is not another pattern, really, like divergent

and convergent evolution, this is when two

organisms are evolving based on the selection

pressures provided by the other. 2 examples:

• Cheetahs and antelopes have both evolved speed

related adaptations as a result of each other’s

speed.

• Flowers and their pollinators. Great example.

3:40

https://www.youtube.com/watch?v=yFftHXbjEQA

• Traditional evolutionary

trees diagram the

diversification of species as

a gradual divergence over

long spans of time.

• This assumes that big changes

occur because of the

accumulation of many small

ones - the gradualism

model. Like sharks.

3. The punctuated equilibrium model has

stimulated research on the tempo of

speciation


• In the fossil record, many species appear as new forms

rather suddenly (in geologic terms),

• persist essentially unchanged, and

• then disappear from the fossil record.

• Darwin noted this when he remarked that species appear

to undergo modifications during relatively short periods

of their total existence and then remained essentially

unchanged.

• Draw a fossil/rock layers map to show this idea.

• He could not explain this fossil evidence in his

gradualism theory, but we have learned much since then.


• In the punctuated equilibrium model, the tempo

of speciation is not constant.

• Species undergo most

morphological modifications

when they first bud from

their parent population.

• After establishing themselves

as separate species, they

remain static for the vast

majority of their existence.


Fig. 24.17b

Periods of mass extinction (13:25 – with

Neil deGrasse Tyson) followed by rapid

speciation (:30) do exist in the fossil

record.

Stephan Jay Gould helped pioneer the

idea of punctuated equilibrium.

Let’s watch a bit of video?: The Day the

Mesozoic Died

https://www.youtube.com/watch?v=ENR2KNEAYEw

http://www.pbs.org/wgbh/evolution/library/03/4/l_034_02.html

How did the dinosaurs become extinct?

• Under this model, changes may occur rapidly and gradually during the few thousands of generations necessary to establish a unique genetic identity.

• Species will appear suddenly in rocks of a certain age

• Stabilizing selection may then operate to maintain the species relatively the same for tens to hundreds of thousand of additional generations until it finally goes extinct.

• Another neat example of how science keeps adding pieces to the puzzle. FSU link


https://www.washingtonpost.com/news/speaking-of-science/wp/2017/01/03/dinosaurs-took-months-to-hatch-out-of-their-eggs-that-may-have-doomed-them/?utm_term=.d9e7cba7a8da

• The Darwinian concept of “descent with

modification” can account for the major

morphological transformations of macroevolution.

• It may be difficult to believe that a complex organ like

the human eye could be the product of gradual

evolution, rather than a finished design created specially

for humans.

• However, the key to remember is that that eyes do not

need to as complicated as the human eye to be useful to

an animal.

Most evolutionary novelties are modified

versions of older structures


• We have also discovered genes

(HOX genes) that act as master

switches that turn on and off

whole sets of other genes to

cause big changes such as in

development. Mutations in

these genes can cause big

changes very quickly.


Critique this picture

SC.912.L.15.10: Identify basic trends in

hominid evolution from early ancestors

six million years ago to modern

humans, including

brain size,

Jaw size,

language,

and manufacture of tools.

Video selections

• Great Transitions is best if time (20 min.). It has

don Johansen, etc. with hip and hand and skull

comparisons.

• Great Transformations is shorter (8 min.) and has

some of same Johansen clips.

• You Inner Monkey is also good but longer than

both others.

• Primates are monkeys, lemurs, tarsiers and apes

(including us!). Compared to other mammals…

• Most primates have hands and feet adapted for grasping.

• Relative to other mammals, they have large brains and

short jaws.

• They have flat nails on their digits, rather than narrow

claws.

• Primates also have relatively well-developed parental care

and relatively complex social behavior.

1. Primate evolution provides a context for

understanding human origins


• The oldest known

anthropoid fossils,

from about 45

million years ago,

support the

hypothesis that

tarsiers are the

prosimians most

closed related to

anthropoids.


Fig. 34.35

• The earliest primates were probably tree dwellers,

shaped by natural selection for arboreal (tree) life.

• The grasping hands and feet of primates are adaptations

for hanging on to tree branches.

• The thumb is relatively mobile and separate from the

fingers in all primates, but a fully opposable thumb is

found only in anthropoid primates.

• The unique dexterity of humans, aided by distinctive

bone structure at the thumb base, represents descent

with modification from ancestral hands adapted for

life in the trees.

Copyright © 2002 Pearson Education, Inc.,

• Other primate features also originated as

adaptations for tree dwelling.

• The overlapping fields of vision of the

two eyes (binocular vision) enhance

depth perception, an obvious advantage

when brachiating (tree climbing).

• Excellent hand-eye coordination is also

important for arboreal maneuvering.


• In the continuity of life spanning over 3.5 billion

years, humans and apes have shared ancestry for all

but the last few million years.

• Paleoanthropology is the study of human origins

and evolution.

• Paleoanthropology focuses on the tiny fraction of geologic

time during which humans and chimpanzees diverged

from a common ancestor.

2. Humanity is one very young twig on the

vertebrate tree


• Paleoanthropology has a checkered history with

many misconceptions about human evolution

generated during the early part of the twentieth

century that still persist in the minds of the general

public, long after these myths have been debunked

by fossil discoveries.

• First, our ancestors were not chimpanzees or any

other modern apes.

• Chimpanzees and humans represent two divergent

branches of the hominoid tree that evolved around 7

million years ago from a common ancestor that was

neither a chimpanzee nor a human.


• Secondly, human evolution did not occur as a

ladder with a series of steps leading directly from

an ancestral hominoid to Homo sapiens.

• If human evolution is a parade, then many splinter

groups traveled down dead ends and several different

human species coexisted.

• Human phylogeny is more like a multibranched bush

with our species as the tip of the only surviving twig.


SC.912.L.15.10: Identify basic trends in

hominid evolution from early ancestors

six million years ago to modern

humans, including

brain size,

Jaw size,

language,

and manufacture of tools.

Items will not require memorization of the names of specific human fossils or the names of the different hominid species.

Items will not require memorization of the names of specific human fossils or the names of the different hominid species.


Fig. 34.38

• Third, the various human characteristics, such as

upright posture and an enlarged brain, did not

evolve in unison. Bipedalism was first.

• Our pedigree includes ancestors who walked upright but

had brains much less developed than ours, suggesting

that upright walking (bipedalism) set the stage for

the evolution of larger brains.

• After dismissing some of the folklore on human

evolution, we must admit that many questions

about our own ancestry remains.


• Human evolution is marked by the evolution of

several major features.

• Brain Size. Based on skull measurements, researchers

have estimated that brain size in hominoids tripled over

the past 6 million years.

• It increased from about 400-450 cm3 in hominoids

(and similar to modern chimpanzees) to about 1,300

cm3 in modern humans.

• Jaw Shape. Our hominoid ancestors had longer jaws -

prognathic jaws - than those of modern humans.

• This resulted in a flatter face with more pronounced

chins.


Paedomorphogenesis, or Neoteny

• Neoteny is the maintenance of juvenile

characteristics into the adult stage, not

uncommon in the animal kingdom.

• Humans are bipedal, neotenous apes, best seen

in skull structure comparisons.

• Bipedal Posture. Based on fossil skeletons, it is clear

that our hominoid ancestors walked on all four limbs

when on the ground, like modern apes.

• The evolution of bipedalism- upright posture and two-

legged walking - is associated with key skeletal

changes seen in early hominid fossils.

• Position of the foramen magnum (where your backbone connects to your

skull) is more centered in humans so the heads sits on top of the spine.

• Feet with arches and a non-opposable big toe

• Longer, stronger legs/leg bones

• Larger muscles on legs – gluts, hamstrings, quads, gastrocnemius

• Wider pelvis, knees close together for support

• S-curve in lumbar spine to support weight above


Cultural evolution events:

• Tool making (wood, bone and metal)

• Language

• Organized hunting and gathering

• Agriculture

• Industrial revolution

• Commerce and technology

• The various pre-Homo hominids are classified in

the genus Australopithecus (“southern ape”) and

are known as australopithecines.

• The first australopithecine, A. africanus, was discovered

in 1924 by Raymond Dart in a quarry in South Africa.

• From this and other skeletons, A. africanus probably

walked fully erect and had humanlike hands and

teeth.

• However, the brain was only about one-third the size

of a modern human’s brain.


• In 1974, a new fossil, about 40% complete, was

discovered in the Afar region of Ethiopia.

• This fossil, nicknamed “Lucy,” was described as a new

species, A. afarensis.

• These were considered to be our direct ancestors, but

are no longer

• It appears they evolved into other Australopithecines,

like africanus, but that they became extinct.


• Based on this fossil and other discoveries, this

species had a brain the size of a chimpanzee, a

prognathic (bigger) jaw, longer arms (for some

level of arboreal locomotion), and sexual

dimorphism more apelike than human.

• However, the

pelvis and skull

bones and fossil

tracks showed

that A. afarensis

walked bipedally.


Fig. 34.39

• In the past few years, paleoanthropologists have

found hominid species that predate A. afarensis.

• An older fossil that is unambiguously more human than

ape is Australopithecus anamensis, which lived over 4

million years ago.

• Other fossils of putative hominids go back 6 million

years, closer to the ape-human split that molecular

systematists estimate occurred about 5 - 7 million years

ago.

• News flash – 2009 – the oldest widely agreed upon

direct ancestor is now called Ardipithecus ramidus,

found in Ethiopia and dating back to 4.4 million years

ago, a full million years older than Lucy.


• The earliest fossils that anthropologists place in

our genus, Homo, are classified as Homo habilis.

• These fossils range in age from 2.5 to 1.6 million years

old.

• This species had less human-like jaws and larger brains

(about 600 - 750 cm3) than australopithecines.

• In some cases, anthropologists have found sharp stone

tools with these fossils, indicating that some hominids

had started to use their brains and hands to fashion

tools.

• These, however, were NOT our direct ancestors.


• Homo erectus was the first hominid species to

migrate out of Africa, colonizing Asia and Europe.

• They lived from about 1.8 million to 500,000 years ago.

• Fossils from Asia are known by such names as

“Beijing man” and “Java Man”.

• In Europe, H. erectus gave rise to the humans known

as Neanderthals.

• Compared to H. habilis, H. erectus was taller, had a

larger brain (averaging about 1,100 cm3), and had about

the same level of sexual dimorphism as modern

humans.


• The other hypothesis, the “Out of Africa” or replacement hypothesis, argues that all Homosapiens throughout the world evolved from a second major migration out of Africa that occurredabout 100,000 years ago.

• This migration completely replaced all the regional populations of Homoderived from the firsthominid migrations.


Fig. 34.41b

• 2010 update – new DNA sequence studies strongly indicate

some hybridization between Neanderthals and Homo sapiens.

It always changes!!

• 2011 update – a newly found group called Denisovans also

appear to have interbred with us. This info comes from DNA

found in a fingertip fossil!

• Depending on your ancestry, you may have varying amounts of

modern human, Neanderthal and Denisovan DNA.

• Will we continue to evolve?


Here are the traits the EOC may ask you

about

• This is what separates modern humans like us

from our ancestors:

• Larger brain

• Smaller, shorter jaws

• Language

• Complex tool manufacture

Fossil evidence suggests that a number of

members of one fish species from an ancient

lake in Death Valley, California, became several

isolated species. Of the following, which best

explains the cause of the speciation?

• A. episodic isolation

• B. temporal isolation

• C. geographic isolation

• D. behavioral isolation

A species of finch has been studied on one of the geographically isolated

Galapagos Islands for many years. Since the island is small, the lineage of

every bird for several generations is known. This allows a family tree of

each bird to be developed. Some family groups have survived and others

have died out. The groups that survive probably have

A. Interbred with other species

B. Been attacked by more predators

C. Found new places on the island to live

D. Inherited some advantageous variations

Documents

The Origin of New Species · • Adaptive radiation is divergent evolution that has resulted in the formation of, at the very least, new ... and reptiles (swimming dinosaurs with