the diversity of life on earth
DESCRIPTION
How did life on earth begin? What is life? Life is defined by the ability to replicate and by the presence of some sort of metabolic activity.TRANSCRIPT
Day 17 November 4th Chapter 10 - The Origin and Diversification of Life on Earth
Dr. Amy B HollingsworthThe University of Akron
Fall 2014
Chapter 10: The Origin and Diversification of Life on Earth
Understanding biodiversityLectures by Mark Manteuffel, St. Louis Community College
Be able to describe how:
Life on earth most likely originated from nonliving materials.
Species are the basic units of biodiversity.
Evolutionary trees help us conceptualize and categorize biodiversity.
Be able to describe:
Macroevolution and the diversity of life.
An overview of the diversity of life on earth.
10.1–10.2
Life on earth most
likely originated from
non-living materials.
10.1 Complex organic molecules arise in non-living environments.
Phase 1: The Formation of Small Molecules Containing Carbon and Hydrogen
The Urey-Miller Experiments
The first demonstration that complex organic molecules could have arisen in earth’s early environment
Life on earth most likely originated from nonliving materials.
10.2 Cells and self-replicating systems evolved together to create the first life.
Enzymes Required
Phase 2: The formation of self-replicating, information-containing molecules.
RNA appears on the scene.
RNA can catalyze reactions necessary for replication.
The “RNA World” Hypothesis
A self-replicating system
A precursor to cellular life?!
RNA-based life and DNA-based life
What Is Life?
Self-replicating molecules?
How do we define life?
Life Is Defined by Two Characteristics
1. The ability to replicate
2. The ability to carry out some sort of metabolism
Phase 3: The Development of a Membrane, Enabling Metabolism, and Creating the First Cells
Membranes make numerous aspects of metabolism possible.
How did the first cells appear?
Spontaneously?
Mixtures of phospholipids
Microspheres
Compartmentalization within cells
10.3–10.6
Species are the
basic units of
biodiversity.
10.3 What is a species?
Biological Species Concept
Species: different kinds of organisms
Species are natural populations of organisms that:• Interbreed with each other or could possibly
interbreed• Cannot interbreed with organisms outside their
own group (reproductive isolation)
Two Key Features of the Biological Species Concept:
1. Actually interbreeding or could possibly interbreed
2. “Natural” populations
Barriers to Reproduction1. Prezygotic barriers2. Postzygotic barriers
Prezygotic Barriers
Make it impossible for individuals to mate with each otheror
Make it impossible for the male’s reproductive cell to fertilize the female’s reproductive cell
These barriers include:
Courtship rituals
Physical differences
Physical or biochemical factors involving gametes
Postzygotic Barriers
Occur after fertilization
Generally prevent the production of fertile offspring
Hybrids
10.4 How do we name species?
We need an organizational system!
Carolus Linnaeus and Systema Naturae
A scientific name consists of two parts:1. Genus2. Specific epithet
Hierarchical System
Inclusive categories at the top…
…leading to more and more exclusive categories below
10.5 Species are not always easily defined.
Difficulties in Classifying Asexual Species
Does not involve fertilization or even two individuals
Does not involve any interbreeding
Reproductive isolation that is not meaningful
Difficulties in Classifying Fossil Species
Evidence for reproductive isolation???
Difficulties in Determining When One Species Has Changed into Another
It may not be possible to identify an exact point at which the change occurred.
Chihuahuas and Great Danes generally can’t mate.
Does that mean they are different species?
Difficulties in Classifying Ring Species
Example: insect-eating songbirds called greenish warblers
Unable to live at the higher elevations of the Tibetan mountain range
Live in a ring around the mountain range
Difficulties in Classifying Ring Species
Warblers interbreed at southern end of ring.
The population splits as the warblers move north along either side of mountain.
When the two “side” populations meet at the northern end of the ring, they can’t interbreed.
What happened?!
Difficulties in Classifying Ring Species
Gradual variation in the warblers on each side of the mountain range has accumulated.
The two populations that meet have become reproductively incompatible.
There is no exact point at which one species stops and the other begins.
Difficulties in Classifying Hybridizing Species
Hybridization• The interbreeding of closely related species
Have postzygotic barriers evolved?
Are hybrids fertile?
Morphological Species Concept
Focus on aspects of organisms other than reproductive isolation as defining features
Characterizes species based on physical features such as body size and shape
Can be used effectively to classify asexual species
10.6 How do new species arise?
Speciation
One species splits into two distinct species.
Occurs in two distinct phases
Requires more than just evolutionary change in a population
Allopatric Speciation
Speciation with geographic isolation
Speciation without Geographic Isolation
Polyploidy
Error during cell division in plants
Chromosomes are duplicated but a cell does not divide.
This doubling of the number of sets of chromosomes is called polyploidy.
Polyploidy The individual with four sets can no longer
interbreed with any individuals having only two sets of chromosomes.
Self-fertilization or mating with other individuals that have four sets can occur.
Instant reproductive isolation, considered a new species
10.7–10.9
Evolutionary trees
help us
conceptualize and
categorize
biodiversity.
10.7 The history of life can be imagined as a tree.
Systematics and Phylogeny
Systematics names and arranges species in a manner that indicated:
• The common ancestors they share • The points at which they diverged from each other
Systematics and Phylogeny
Phylogeny• Evolutionary history of organisms
Nodes • The common ancestor points at which species diverge
10.8 Evolutionary trees show ancestor-descendant relationships.
Are humans more advanced, evolutionarily, than cockroaches?
Can bacteria be considered “lower” organisms?
Monophyletic Groups
A group in which all of the individuals are more closely related to each other than to any individuals outside of that group
Determined by looking at the nodes of the trees
Constructing evolutionary trees requires comparing similarities and differences between organisms.