Lecture 10: Speciation

Question 1

If gene flow STOPS allele frequencies in isolated
populations can diverge
- The populations begin to evolve independently
– Divergence may occur as a result of mutation, natural selection, and genetic drift

T or F

Answer 1

True

Question 2

DEF: This genetic divergence may eventually result

Answer 2

Speciation

Question 3

Speciation is a s____ event that creates two or
more distinct species from an ancestral species
– Can occur gradually or abruptly
– When speciation is complete,
▪ a new branch has been added to the tree of life

Answer 3

Splitting

Question 4

DEF: as an evolutionarily independent population or group of populations

Answer 4

Species

Question 5

Biologists commonly use four criteria for
identifying species (4 points)

Answer 5

1. The biological species concept
2. The morphological species (morphospecies) concept
3. The ecological species concept
4. The phylogenetic species concept

Question 6

What concept explains the the main criterion for identifying species is REPRODUCTIVE ISOLATION?
-Results in lack of gene flow between populations
– Members of the populations do not interbreed, or fail to produce viable, fertile offspring after mating

Answer 6

The biological species concept

Question 7

Biologists categorize the mechanisms that stop
gene flow between populations (i.e., reproductive
isolation) as either: (2 points)

Answer 7

1. Prezygotic isolation
2. Postzygotic isolation

Question 8

DEF: Individuals of different species are prevented from mating successfully

Answer 8

Prezygotic isolation

Question 9

DEF: The hybrid offspring do not survive or reproduce

Answer 9

Postzygotic isolation

Question 10

The biological species concept has
disadvantages:
– Reproductive isolation cannot be evaluated in
▪ Fossils
▪ Species that reproduce asexually
– It cannot be applied to populations that do not overlap
geographically

T or F

Answer 10

True

Question 11

Which concept explains that individual lineages differ in size, shape, or other morphological features
- Distinguishing features most likely arise if populations are independent and isolated from gene flow
-Useful when there is no data on the extent of gene flow
– Equally applicable to sexual, asexual, and fossil
species

Answer 11

The morphospecies concept

Question 12

Disadvantages:
– One p______ species may be classified as more
than one species
– It cannot identify c_____ species that differ in non-
morphological traits
– The features used to distinguish species under this
concept are subjective

Answer 12

Polymorphic, cryptic

Question 13

A set of organisms:
– exploiting a single set of resources
– Having the same range of environmental tolerances
– Facing the same predators and parasites
* Emphasizes natural selection, adaptive traits

Most useful for identifying asexually reproducing
species
– Bacteria, archaea asexual eukaryotes

• Disadvantages:
  – Cannot be defined by reproductive isolate from other
  species
  – Distinctions among species maintained by adaptation to different ecological conditions

T or F

Answer 13

True

Question 14

Identifies species based on evolutionary history
– Based on the rationale that all species are related by c______ ancestry

Answer 14

Common

Question 15

On phylogenetic trees, a m_____ group
consists of an ancestral population plus all of its
descendants
– Also called a c_____ or l_____

Answer 15

Monophyletic, clade, lineage

Question 16

DEF: Monophyletic groups are identified by s_____
(“unique forms”)
- Homologous traits found in common ancestor and
descendants but missing in more distant ancestor
– Example: Fur or milk-producing glands in mammals
– Therefore, a species is defined as the smallest
MONOPHYLETIC GROUP on the tree of life

Answer 16

Synapomorphies

Question 17

The phylogenetic species concept has two distinct
advantages:
1. It can be applied to any type of population (e.g., fossil,
asexual, or sexual)
2. It is logical because different species have different
synapomorphies due to lack of gene flow and
independent evolution

The phylogenetic species concept also has
disadvantages:
– Phylogenies are currently available for only a tiny
(though growing) subset of populations on the tree of
life
– Critics point out that it would probably lead to
recognition of many more species than either of the
other species concepts
▪ But this may better reflect the extent of life’s diversity

T or F

Answer 17

True

Question 18

DEF: what are populations that
– Live in discrete geographic areas
– Have distinguishing features
– Are not distinct enough to be considered a separate
species
– Can interbreed if geographical barriers are removed

Answer 18

Subspecies

Question 19

Researchers had traditionally named six
subspecies of seaside sparrows
– Live in salt marshes along the Atlantic and Gulf coasts
– Populations are physically isolated from one another
– Differ by colouration and songs

T or F

Answer 19

True

Question 20

In 1980, only six individuals—all males—remained
of the dusky seaside sparrow subspecies
* Biologists launched a conservation program under
the Endangered Species Act
– The plan was to breed the males with females from the
nearby subspecies
– The hybrid offspring would be used in a reintroduction
program by preserving as much genetic diversity as
possible by reestablishing a population of dusky-like
birds

T or F

Answer 20

True

Question 21

Phylogenetic analysis showed
– only two distinct monophyletic groups of seaside
sparrows exist
* The dusky seaside sparrow was
– genetically indistinguishable from the other Atlantic
Coast sparrows
– but different from sparrows from the Gulf Coast lineage
– by crossing females from the Gulf Coast lineage with
dusky seaside males
▪ dusky seaside sparrow went extinct

T or F

Answer 21

True