Species and Speciation Flashcards
How were plants named up until the 18th century?
- Local scientists would have their own names for common plants and would use them when talking w other scientists from different areas.
- The scientific names given to plants consisted of very long strings of Latin words that could be changed at the will of the person studying them.
Frequently, when a scientist would discover a name used in a different locale for a plant they already knew, they would just add the new name to the existing one. Some plants had names consisting of 15-20 words!
What did Carolus Linnaus do?
- Carolus Linnaeus began creating a set rules for the naming of plants.
- He classified and named over 12,000 plants+animals
- Did not invent binomial nomenclature (two descriptive words given to identify a species), but he used it to such a degree that most give him credit for establishing its’ use.
- Provided us with one of our first real taxonomic hierarchies.
This was done in the 1700s.
Why did Carolus Linnaeus classify plants?
- He wanted to help standardize the naming of plants for scientific purposes
- He felt that by organizing and naming all the plants (and then animals) in the world, he (and scientists) would have a better understanding of God, and thus, be closer to God.
Taxonomic Hierarchy
- A system of classifying and naming species for the purpose of understanding and establishing relatedness between species or larger groupings.
- The 7 basic levels include: Kingdom, Phylum, Class, Order, Family, Genus and Species.
Some systems of classification use the prefixes super- and sub- to describe further refinement of groupings above and below a certain level.
How do we name an individual type of organism?
- With Genus and Species.
- Are either underlined or written in italics (because they are Latin).
- The genus name has a capitalized first letter; the species name has a lowercase first letter)
How many Kingdoms are there?
- Linnaeus divided all life into Plantae and Animalia.
- Some have divided into Plantae, Animalia, and Fungi.
- Until very recently, the most commonly used hierarchy included Monera, Protista, Plantae, Fungi, and Animalia.
- Now, many use the Domains (lvl above kingdom) Bacteria and Archae (instead of Monera); as well as the Domain Eukarya (which contains plants, fungi, animalia, and protista kingdoms).
White tailed deer order->species
- Order: Artiodactyla (quadruped w even # of digits)
- Family: Cervidae (bony antlers)
- Genus: Odocoileus (small groups, white hair under tail)
- Species: virginianus (antler points extend from a single main beam)
Scientific name is Odocoileus Virginianus
Species definition
- A species is an evolutionarily independent group; mutation, selection, and drift act on the group independently of what’s happening in other groups.
Species notes
- Gene flow between groups causes allele frequencies to be the same.
- If gene flow stops, then mutation, selection, and drift begin to work. (Although these things are working all the time at some level).
- If new alleles arise in one group, there is no way for it to get to the other group.
- If allele frequencies change sufficiently over time, populations become distinct species.
Biological Species Concept
- If two populations do not interbreed in nature, or do so but fail to produce viable offspring- they are separate species
- Is problematic for distinguishing species in the fossil record and for organisms whose populations do not overlap (they cannot interbreed).
Prezygotic Isolation
This term is used with the Biological Species Concept
- Prevention of individuals from mating
- Temporal- breeding at different times
- Habitat- breed in different habitats
- Behavioral- courtship displays differ
- Gametic barrier- Eggs and sperm are incompatible
- Mechanical- Genitalia incompatible
ex. lightning bugs
Postzygotic Isolation
This term is used with the Biological Species Concept
- Offspring of individuals do not survive or reproduce
- Hybrid viability- Offspring die as embryos
- Hybrid sterility- Offspring mature, but are sterile
Morphospecies Concept
- Says that differences between groups in size, shape, or other morphological features (and sometimes in behaviors) indicate the two groups are different species
- Logic is that in order to be this different, the populations must have been apart and separated long enough to become distinct species.
- The morphospecies concept works with sexual, asexual, and fossilized/extinct species.
- Problems arise because traits are often subjective. Differences seen between groups of organisms may represent variation within the species, the effects of genetic drift, mutations, and/or natural selection.
Example: Cooper’s and Sharp-shinned hawks
Phylogenetic Species Concept
- Phylogenetics is the reconstruction of the evolutionary history of populations
- This concept takes into account a variety of traits specific to the population in order to establish relatedness between groups, and therefore, distinction between them.
- Species are determined by populations having distinctions from other populations (morphological, behavioral, genetic).
Phylogenic analysis results in a phylogenetic tree
Phylogenetic Tree
- A branching diagram that depicts relatedness/distinction among groups.
- Branches within the tree represent a population through time.
- Nodes (where branches come together) are points in time when an ancestral group split into 2 or more descendant groups, each group represented by each branch.
- Terminal Nodes at the ends of branches represent a group (species, or larger, living or extinct).
Phylogenetic analysis methods
Phenetics
The grouping of species by similarity of traits, whether those traits are ancestral or more recently derived.
Phylogenic Analysis Methods
Cladistics
Grouping of species by shared, recently derived characters only
-Monophyletic group- most recent common ancestor and all its descendants
-Paraphyletic group- most recent common ancestor and not all of its descendants. (Not useful to study phylogenies, but used when trying to clarify the loss of evolved traits and convergence)
Cladistics is largely based on the idea that species with recently evolved traits are likely closely related. The independent evolution of a trait in multiple genetic lines is much less likely than it evolving once in an ancestory and that ancestor passing that trait to its various descendent lines, especially for those traits that are relatively recently evolved.
Pros and cons with phylogenetics
Cons:
* Because we can track genetic differences between almost all populations within a species, (and even between individuals within a population), we could end up with a huge # of species (each individual being its’ own species)
* If you do not choose the correct suite of traits to compare, you could end up with garbage
Pro:
* The use of phylogenetics to solve problems of maintaining genetic diversity is highly effective if done correctly.
Homology
traits are similar due to a shared ancestry
Homoplasy
traits are similar due to other reasons than common ancestry
Convergent Evolution
The independent evolution (by natural selection) of similar traits in distantly related organisms, where the common ancestor does not have the trait
Convergent Evolution is the most common cause of homoplasy
Parsimony
the most likely explanation or pattern is the one that implies the least amount of change (ex. the simplest)
How do we get new species?
- The creation of new species is a process based on isolation of 1 or more groups from an ancestral group, and the genetic divergence between the new and ancestral groups.
- Speciation occurs when subgroups are isolated reproductively and divergence occurs during this separation.
- The ancestral population may continue to look roughly the same for a very long time (they maintain their species identity), while the new group diverges dramatically. Or the two groups may diverge more or less equally.
Speciation can occur in Allopatric and Sympatric populations
Speciation is not one group separating into two new species then those separating into two new species, etc.
Allopatric speciation
- Occurs when subpopulations are separated by some physical barrier.
- The two subpopulations remain reproductively isolated (no gene flow) and, over time, diverge from each other (due to genetic drift, mutations, or natural selection differences between populations).
Method (Causes) of Allopatric Speciation
Dispersal
When a group emigrates from an area, and they are isolated long enough to have allele changes that eventually lead to a new species.
Method (Causes) of Allopatric Speciation
Vicariance
- When a population is divided by a change in the geologic landscape.
- If the sub populations remain separated long enough, allele frequencies will change enough to call then separate species.
Sympatric Speciation
- Occurs when new species are created in areas where there is no physical barrier between supopulations, meaning they could interbreed.
- If parts of a population prefer certain foods or habitats, they may eventually become separate species
- Ex. Golden-winged and Blue-winged warblers: where they overlap they prefer different habitats; they did this long enough to separate morphologically and genetically (but not biologically)
Traditionally scientists thought you couldn’t get sympatric speciation, that gene flow between groups would overwhelm differences that occur.
What happens if newly formed species come back into contact?
Reinforcement of Species
If the populations can interbreed, produce young, and hybrids have suppressed fitness (sterile or lowered fitness), then selection would favor those that do not interbreed. Further separation will occur.
What happens if newly formed species come back into contact?
Hybrid zones
- Areas where 2 populations overlap and hybrids exist.
- May be small or large, short-lived or long-lived.
What happens if newly formed species come back into contact?
New Species through Hybridization
- Hybrids contain a unique blend of alleles from parents and therefore different characteristics.
- If these traits can be selected for, then the genes are passed on to the next generation.
- A new species may be created as a result.
