Chapter 15 – Speciation and Phylogeny Flashcards
What is speciation?
When a population has changed enough that it diverges from its present species and becomes a new species.
Can you tell which species an organism is part of just based on appearance?
No, some species vary in appearance (humans, dogs). Some different species look nearly identical (East and West meadowlarks)
What are the four species concepts? Which is most commonly used?
Biological, morphological, ecological, phylogenetic.
Morphological is most common.
What is the biological species concept?
A species is a group or population whose members have the potential to interbreed in nature and produce fertile offspring.
What are some difficulties with the biological species concept?
Some animals usually seen as different species (like grizzly and polar bears) can produce fertile offspring (a Nanulak). Also with fossils and asexual organisms, we don’t know which could interbreed.
What is the morphological species concept? What is one problem with it?
For fossils and living animals, classification is based mainly on physical traits such as shape, size, appearance, etc.
Sometimes we disagree on which features matter in distinguishing a species.
What is the ecological species concept?
It identifies species in terms of their ecological niches (the role they play in an ecosystem). Species generally have different adaptations so they don’t directly compete and have niches instead.
What is the phylogenic species concept? What is one problem with it?
A species is the smallest group of individuals that share a common ancestor and thus form one branch on the tree of life.
Disagreement on the amount of difference required to separate species.
What is phylogeny?
The evolutionary history of a species or group of related species.
Phylon = tribe, genesis = origin.
What concepts can we use to identifying species in organisms that reproduce asexually?
The morphological, ecological or phylogenetic concepts
How have species in Lake Victoria changed in recent decades?
200 species of cichlid fish have been lost in part due to the introduction Nile perch, increasingly murky waters, pollution, etc. Some different species have begun interbreeding and making viable offspring.
Can reproductive isolation lead to new species?
Yes!
What prevents closely related species from mating and producing offspring?
Reproductive barriers which can be prezygotic (before fertilization) or postzygotic (after fertilization).
What are the 5 main types of prezygotic barriers?
- Habitat isolation
- Temporal isolation (breeding at different times)
- Behavioural isolation (no mate recognition)
- Mechanical isolation (reproductive parts don’t fit/align)
- Gametic isolation (sperm won’t fertilize another species egg)
What are the 3 main types of postzygotic barriers?
- Reduced hybrid viability (hybrid dies young/before birth)
- Reduced hybrid fertility
- Hybrid breakdown (the hybrid’s offspring are not successful)
What are the two key types of speciation that can arise?
Allopatric and Sympatric.
What is allopatric speciation?
Allos = other, patra = fatherland.
Species are geographically separated from one another.
What is sympatric speciation?
Syn = together, patra = fatherland
A new species arises within the same geographical area as its parent species.
How large does a geographic barrier need to be before it effectively separates organisms into different populations?
It depends on the species!
i.e. pretty small for mice, really big for birds.
Do geographic barriers always result in new species?
No. There must also be some selective pressure in the new environment.
i.e. a different food source, predators, pollinators.
Where is allopatric speciation most commonly identified?
On isolated island chains inhabited by unique species. Especially if the islands are physically diverse and far enough apart so populations evolve in isolation but close enough for occasional migration.
What is adaptive radiation? What’s a good example of this?
The evolution of many diverse species from a common ancestor. Darwin’s finches!
What differentiates Darwin’s 14 finches? Which type of speciation is this?
Their feeding habits and their beaks that are specialized for what they eat on each island.
Allopatric speciation.
How do Darwin’s finches continue to evolve?
Their beak sizes responding to precipitation patterns, becoming larger during droughts. Also some species occasionally interbreed.
What type of speciation is responsible for the majority of species on the planet?
Allopatric speciation.
What can cause sympatric speciation (3)?
Habitat differentiation, sexual selection, and when errors in mitosis/meiosis lead to polyploidy (most common in plants).
How can food sources cause habitat differentiation?
Subgroups may adapt for different food sources in different habitats (i.e. near shore or deep water) this may isolate the gene pools without a geographic barrier.
Both habitat differentiation and sexual selection can contribute to the formation of ______________ _______________ between allopatric populations.
reproductive barriers
What is a hybrid zone? How does this impact speciation?
Areas where the hybrid offspring are prevalent.
Can combining the parent species back into one or create a distinct hybrid population (if the offspring are fertile).
What is a common form of sympatric speciation in plants? What generally causes this?
Polyploidy. A cell fails to divide after chromosome duplication creating a 4n (tetraploid) cell which could produce a 4n flower and then a viable 4n seed through self-fertilization.
Why does polyploidy instantly create new species?
A 4n plant makes 2n gametes which if combined with a regular 1n gamete, makes a 3n plant. Triploid offspring are sterile. So 4n is reproductively isolated from its 2n parent plant.
Most hybrid animals cannot reproduce, but what about plants?
With an odd number of chromosomes, a hybrid plant is sterile. But an error in cell division could duplicate the chromosomes making it 2n and a fertile hybrid.
Most plant species trace their origin to __________ speciation.
polyploid (a type of sympatric speciation)
What do we mean by punctuated equilibrium?
When a species has long periods with little change punctuated by abrupt episodes of rapid change.
Is the rate of speciation fast or slow?
Either! New species can appear slowly over millions of years or suddenly as in the case of punctuated equilibria or polyploidy in plants.
How can we study the evolutionary history of a species (3 sources of info)?
Fossils, homologies, molecular systematics.
What do we mean by convergent evolution?
Species from different evolutionary branches may resemble one another if they live in similar environments and natural selection has favoured similar adaptations.
What is an analogous characteristic?
A similarity between two species due to convergent evolution, rather than descent from a common ancestor.
What are homologous characteristics/structures?
Features that often have different functions, but that are structurally similar because of a common ancestor. i.e. mammal forelimbs have similar bones, muscles, and nerves.
How can we determine if organisms similarities are analogous or homologous?
Some assumptions – if the structures are highly complex and match for many details, analogy is unlikely.
What are systematics?
A scientific discipline that classifies organisms and determines their evolutionary relationships.
How do we use systematics to classify life?
Each species gets a binomial name: Genus species
It also has a full hierarchical classification (genus, family, order, etc.) which aims to show evolutionary relationships.
What is cladistics? What are clades?
The most widely used method in systematics where common descent is used to group organisms into clades (a group of species that includes an ancestral species and all its descendants).
What are shared ancestral characters?
A character shared by a particular clade that originated in an ancestor that is not a member of the clade.
i.e. backbones in mammals are also seen in reptiles.
What are shared derived characters?
An evolutionary novelty that is unique to a particular clade.
i.e. hair in mammals
How do we determine phylogenies?
By using shared characteristics. More similarities = more related.
What is a taxon (plural taxa)?
A taxonomic group of any rank, such as a species, genus, family or class.
What is an out-group (in terms of phylogeny)?
A taxon or group of taxa that diverged before the lineage containing the group of species being studied.
What is an in-group (in terms of phylogeny)?
The group of taxa whose evolutionary relationships are being determined.
How are phylogenic trees structured? What do nodes represent?
Each tree is a series of 2-way branches. Each branch point is a node and represents the divergence of two groups from a common ancestor.
What is a monophyletic taxon?
A clade (a group of species that includes an ancestral species and all its descendants). We’re saying there’s a relationship among all of the organisms within the clade.
What is molecular systematics?
Using DNA or other molecules to infer relatedness.
What’s one cool fact about fungi (related to molecular semantics)?
Molecular level analyses show that fungi are more closely related to animals than to green plants!
What system is currently used for classifying all life.
A 3 domain system. Two domains of prokaryotes – the bacteria and archaea, and one domain of eukaryotes.
What are the two theory for the emergence of the 3 domains?
- Bacteria and archaea emerged early and then eukaryotes emerged from archaea.
- Eukaryotes arose when an early archaean fused with an early bacterium (ring of fire model)
The ______ __ ___ _______ is the source of biological diversity.
Origin of new species.
