Chap.15 Biolog. Diversity, Classification

Chapter 15

What is a species?

= a distinct form of life

Biological species concept

:

species

= a population/group whose members can

interbreed and produce fertile offspring together

Microevolution vs

Macroevolution

:

Macroevolution

= dramatic biological change:

speciation, extinction, evolution of major new

structure

Reproductive Barriers

Reproductive Barriers

Barriers to interbreeding:

Breeding season timing (temporal isolation)

Example: The Red-legged Frog (Rana aurora, left) breeding season lasts from January to March. The closely related Yellow-legged Frog (Rana boylii, right) breeds from late March through May.

Reproductive Barriers

Breeding behavioral differences (ex: bird mating calls, courtship displays)

Different species of bowerbird construct elaborate bowers and decorate them with different colors in order to woo females. The Satin bowerbird (left) builds a channel between upright sticks, and decorates with bright blue objects, while the MacGregor’s Bowerbird (right) builds a tall tower of sticks and decorates with bits of charcoal. Evolutionary changes in mating rituals, such as bower construction, can contribute to speciation.

Reproductive Barriers

Habitat isolation (different habitat conditions even

in same geographic area)

Example: In central and northern California, the Red-legged Frog (Rana aurora) breeds in fast-moving, ephemeral streams. Artificially introduced Bullfrogs (Rana catesbiana) breed in permanent ponds.

The metamorphosis times of the two species' tadpoles are correspondingly different.

Reproductive Barriers

Incompatible reproductive structures [Mechanical Isolation]

Example: In some snail species, the direction of shell coiling is controlled by a single (maternal effect) gene. Snails with left-coiling shells cannot mate with snails having right-coiling shells. This could eventually lead to further differentiation and speciation.

Reproductive Barriers

Infertile hybrid offspring (mule) or unsuccessful development of hybrid offspring

Infertile “mule” offspring

Example: Horses and donkeys are reproductively isolated as

Geographic Isolation may cause speciation

– Geographic changes to earth – Population dispersal

Separated populations may undergo extensive genetic drift and adaptation (this may lead to other reproductive barriers)

Adaptive radiation

Small group arrives in new habitat (ex: recently

formed island)

New groups evolve from common ancestors via

genetic drift and adaptation

– Diverse species will adapt to new diverse

environments

Punctuated equilibrium: Pace of evolution

Long periods of equilibrium

(no change) in fossil

record;

Punctuated equilibrium: Pace of evolution

How can sudden evolution/

speciation occur?

Genetic drift, natural selection act

quickly

(hundreds or

thousands of years) on

populations adapting to

new/changing environments

• Fossil Record: successful

species= 1-5 million years

Evolution pacing models

Steady, small changes

Quick, rapid

adaptation. Well supported in

15.1 Concept Questions

1. Why are donkeys and horses considered different species?

2. How is macroevolution different from microevolution?

3. Give 3 examples of reproductive barriers that may separate two similar species.

4. Why might an island be a likely place for adaptive radiation?

Refinement of existing adaptations

Large changes (macroevolution) may result from accumulated small adaptations

Ex: Mollusk Eyes

– Some species have complex eye structures

– Complex eyes evolved from simpler eye structures

Squid ancestors probably had simpler visual structures

Adaptations of existing

structures to new functions

exoskeletons

Evolved as protection in sea-dwelling creatures (lobster, crab ancestors)

Land arthropods (insects) adapt chitin to avoid water loss

Ex: penguins

Genetic basis for evolutionary

remodeling

Developmental biology can explain some evolved

adaptations

Embryology: study of organisms’ development from fertilized eggs to fully formed adults

Small changes (mutations) to developmental genes

can cause species to develop differently

Example: tree vs. ground salamander

Tree salamander ends foot growth earlier in

development than ground salamander

Concept Questions 15.2

1. How can evolution explain how some organisms

have very simple eyes while others have

complex eyes?

2.

Give an example of evolutionary remodeling of an

existing structure to a new function (don’t use

penguin flippers or chitin!)

3.

Identify one possible event during an organism's

embryonic development that can result in a

Fossils help create a history of life

on Earth

Fossil formation: organism

preserved/petrified in

sedimentary rock, ice, amber

Fossils give clues to body

structures, diet, and

Geologic Time Scale

= Record of earth’s history

Divided into Precambrian,

Paleozoic, Mesozoic Era’s

Eras divided into periods

and epochs

Divisions based on major

macroevolution events:

first cells, first plants, first

animals, major

extinctions, major

Determining fossil age gives

clues to the past

Fossil location tells relative age of fossil

Radiometric dating of rock’s & fossils tells absolute age

– Carbon-14 dating:

Presence of radioactive isotope

used to date organisms from up to 50,000 years ago

– Uranium-238 dating can determine age of older fossils

Continental Drift can cause

macroevolution

=Movement of major land masses (continents) due to tectonic plate movement

*Causes geographic isolation

*Organisms separated for a long time are more distinct (independent evolution)

i.e. Australia has many unique species

*Organisms from areas that were recently connected are more similar

Continental Drift can cause

macroevolution

Pangea (supercontinent):

*Organisms brought together, forced to compete and adapt to drier

conditions

*Formation of Pangea caused mass extinction, also new speciation

Mass Extinctions



New speciation (adaptive radiation)

Earth history has stability

interrupted by several

mass

extinctions

(many species

wiped out)

Loss of bio-diversity usually

followed by

adaptive

radiation

by survivors

dinosaurs, adaptive radiation of mammal species

Concept Check 15.3

1. Which

parts

of organisms are most commonly

found as fossils?

2. What can the fossil record tell us?

3. How are different Era’s

separated

from one

another?

4. How is

relative fossil age

different from

absolute

fossil age

?

Why not common names?

Name the organism below:

Cougar

Mountain Lion

Puma

Mountain screamer

Lion

Big cat

Taxonomy reflects evolutionary

history

Taxonomy

: identification,

naming, classifying species

Universal

scientific name

assigned to each species

Carolus Linnaeus:

binomial

nomenclature

Hierarchy of Classification:

Classification is based on shared

characteristics

Phylogenetic tree

:

reflects branching

evolutionary

relationships

*Closely related

organisms have more

Classification is based on shared

characteristics

Cladistics

: method of

grouping organisms

based on shared

Derived traits

(shared

traits inherited from a

common ancestor)

– Ex: bony spine, fur, skull

structure in Dog and

Sample cladogram

Derived Traits: shared by all

members of branch

Branch point:

represents common ancestor

Cladistics shows some surprising evolutionary relationships

Example: Croc’s more closely related (share more derived characteristics) with birds than with snakes or lizards

Some species share many structures, but not from a

common ancestor:

Convergent evolution:

species in similar

environments evolve similar adaptations: results in

analagous structures

Examples:

– Wings (for flight) in birds and insects

– _{Thylacine and Dingo body structure similar body} structure due to similar role as hunters

Analagous = evolved Apart.

Evolved in S.E. Asia, then

introduced to Australia

Analagous vs homologous structures:

Kangaroo (closer relative of thylacine)

Wolf- close

Classification schemes

Old 2 or 3 Kingdom schemes

:

Plant, Animal, Fungi

5 Kingdom System

All prokaryotes grouped

together (Monerans)

Based on morphology

(observed physical

3 Domain System

Based on DNA analysis

Most accurate based on

evolutionary relationships

Two prokaryote groups: Bacteria, Archaea

Archaea more closely related to Eukaryotes than to other

HW: Concept Check 15.4

1.

Give two reasons why

common names

of

organisms can lead to confusion.

2.

Why are

analogous structures

not useful for

classifying species in an evolutionary context

(compared to

derived traits

)?

3.

What does a

branch

point in a

cladogram

represent?

4.

How does the

three-domain model

of