Chapter 15 – Speciation and Phylogeny

Question 1

What is speciation?

Answer 1

When a population has changed enough that it diverges from its present species and becomes a new species.

Question 2

Can you tell which species an organism is part of just based on appearance?

Answer 2

No, some species vary in appearance (humans, dogs). Some different species look nearly identical (East and West meadowlarks)

Question 3

What are the four species concepts? Which is most commonly used?

Answer 3

Biological, morphological, ecological, phylogenetic.
Morphological is most common.

Question 4

What is the biological species concept?

Answer 4

A species is a group or population whose members have the potential to interbreed in nature and produce fertile offspring.

Question 5

What are some difficulties with the biological species concept?

Answer 5

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.

Question 6

What is the morphological species concept? What is one problem with it?

Answer 6

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.

Question 7

What is the ecological species concept?

Answer 7

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.

Question 8

What is the phylogenic species concept? What is one problem with it?

Answer 8

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.

Question 9

What is phylogeny?

Answer 9

The evolutionary history of a species or group of related species.
Phylon = tribe, genesis = origin.

Question 10

What concepts can we use to identifying species in organisms that reproduce asexually?

Answer 10

The morphological, ecological or phylogenetic concepts

Question 11

How have species in Lake Victoria changed in recent decades?

Answer 11

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.

Question 12

Can reproductive isolation lead to new species?

Answer 12

Yes!

Question 13

What prevents closely related species from mating and producing offspring?

Answer 13

Reproductive barriers which can be prezygotic (before fertilization) or postzygotic (after fertilization).

Question 14

What are the 5 main types of prezygotic barriers?

Answer 14

• 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)

Question 15

What are the 3 main types of postzygotic barriers?

Answer 15

• Reduced hybrid viability (hybrid dies young/before birth)
• Reduced hybrid fertility
• Hybrid breakdown (the hybrid’s offspring are not successful)

Question 16

What are the two key types of speciation that can arise?

Answer 16

Allopatric and Sympatric.

Question 17

What is allopatric speciation?

Answer 17

Allos = other, patra = fatherland.
Species are geographically separated from one another.

Question 18

What is sympatric speciation?

Answer 18

Syn = together, patra = fatherland
A new species arises within the same geographical area as its parent species.

Question 19

How large does a geographic barrier need to be before it effectively separates organisms into different populations?

Answer 19

It depends on the species!
i.e. pretty small for mice, really big for birds.

Question 20

Do geographic barriers always result in new species?

Answer 20

No. There must also be some selective pressure in the new environment.
i.e. a different food source, predators, pollinators.

Question 21

Where is allopatric speciation most commonly identified?

Answer 21

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.

Question 22

What is adaptive radiation? What’s a good example of this?

Answer 22

The evolution of many diverse species from a common ancestor. Darwin’s finches!

Question 23

What differentiates Darwin’s 14 finches? Which type of speciation is this?

Answer 23

Their feeding habits and their beaks that are specialized for what they eat on each island.
Allopatric speciation.

Question 24

How do Darwin’s finches continue to evolve?

Answer 24

Their beak sizes responding to precipitation patterns, becoming larger during droughts. Also some species occasionally interbreed.

Question 25

What type of speciation is responsible for the majority of species on the planet?

Answer 25

Allopatric speciation.

Question 26

What can cause sympatric speciation (3)?

Answer 26

Habitat differentiation, sexual selection, and when errors in mitosis/meiosis lead to polyploidy (most common in plants).

Question 27

How can food sources cause habitat differentiation?

Answer 27

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.

Question 28

Both habitat differentiation and sexual selection can contribute to the formation of ______________ _______________ between allopatric populations.

Answer 28

reproductive barriers

Question 29

What is a hybrid zone? How does this impact speciation?

Answer 29

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).

Question 30

What is a common form of sympatric speciation in plants? What generally causes this?

Answer 30

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.

Question 31

Why does polyploidy instantly create new species?

Answer 31

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.

Question 32

Most hybrid animals cannot reproduce, but what about plants?

Answer 32

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.

Question 33

Most plant species trace their origin to __________ speciation.

Answer 33

polyploid (a type of sympatric speciation)

Question 34

What do we mean by punctuated equilibrium?

Answer 34

When a species has long periods with little change punctuated by abrupt episodes of rapid change.

Question 35

Is the rate of speciation fast or slow?

Answer 35

Either! New species can appear slowly over millions of years or suddenly as in the case of punctuated equilibria or polyploidy in plants.

Question 36

How can we study the evolutionary history of a species (3 sources of info)?

Answer 36

Fossils, homologies, molecular systematics.

Question 37

What do we mean by convergent evolution?

Answer 37

Species from different evolutionary branches may resemble one another if they live in similar environments and natural selection has favoured similar adaptations.

Question 38

What is an analogous characteristic?

Answer 38

A similarity between two species due to **convergent evolution**, rather than descent from a common ancestor.

Question 39

What are homologous characteristics/structures?

Answer 39

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.

Question 40

How can we determine if organisms similarities are analogous or homologous?

Answer 40

Some assumptions – if the structures are highly complex and match for many details, analogy is unlikely.

Question 41

What are systematics?

Answer 41

A scientific discipline that classifies organisms and determines their evolutionary relationships.

Question 42

How do we use systematics to classify life?

Answer 42

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.

Question 43

What is cladistics? What are clades?

Answer 43

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).

Question 44

What are shared ancestral characters?

Answer 44

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.

Question 45

What are shared derived characters?

Answer 45

An evolutionary novelty that is unique to a particular clade. i.e. hair in mammals

Question 46

How do we determine phylogenies?

Answer 46

By using shared characteristics. More similarities = more related.

Question 47

What is a taxon (plural taxa)?

Answer 47

A taxonomic group of any rank, such as a species, genus, family or class.

Question 48

What is an out-group (in terms of phylogeny)?

Answer 48

A taxon or group of taxa that diverged before the lineage containing the group of species being studied.

Question 49

What is an in-group (in terms of phylogeny)?

Answer 49

The group of taxa whose evolutionary relationships are being determined.

Question 50

How are phylogenic trees structured? What do nodes represent?

Answer 50

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.

Question 51

What is a monophyletic taxon?

Answer 51

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.

Question 52

What is molecular systematics?

Answer 52

Using DNA or other molecules to infer relatedness.

Question 53

What's one cool fact about fungi (related to molecular semantics)?

Answer 53

Molecular level analyses show that fungi are more closely related to animals than to green plants!

Question 54

What system is currently used for classifying all life.

Answer 54

A 3 domain system. Two domains of prokaryotes – the bacteria and archaea, and one domain of eukaryotes.

Question 55

What are the two theory for the emergence of the 3 domains?

Answer 55

1. Bacteria and archaea emerged early and then eukaryotes emerged from archaea. 2. Eukaryotes arose when an early archaean fused with an early bacterium (ring of fire model)

Question 56

The ______ __ ___ _______ is the source of biological diversity.

Answer 56

Origin of new species.