BIO120 Final

Taxonomic (or morphological)

Based primarily on distinct morphological differences

Biological

Based on inter-fertility (cross-ability) among individuals

Ernst Mayr

Wrote the book Animal and Species Evolution, was convinced that the discontinuities of nature are not arbitrary, but an objective fact

Darwin only explained

how a single species changes over time

Darwin did not explain

how a species splits into two different species

speciation

formation of new species

species

A group of similar organisms that can breed and produce fertile offspring

biological species concept

An idea created by Ernst Mayr that a group of interbreeding natural populations that are reproductively isolated from other such groups

What are the two main modes of speciation

Allopatric and sympatric

allopatric

geographically separate

sympatric

geographically overlapping

What causes reproductive isolation

finding a compatible mate mating & fertilization

development of zygote

adult growth & survival reproduction & fertility of offspring

reproductive isolation

separation of species or populations so that they cannot interbreed and produce fertile offspring

Premating isolation

Prevents zygote formation - mechanical/prevention of gamete fusion

Postmating isolation

prevents successful fertilization and development, even though mating may have occurred

Speciation involves

the evolution of reproductive isolation between populations

Douglas Schemske

Premating isolation in species of monkey flower:

pollinator preferences & altitude

Why are hybrids of monkey flower not seen in the field

because of elevational separation & pollinator preferences

the more _____________ pairs of flies are the more likely they are to be ______________

genetically differentiated, reproductively isolated

Genetic distance

measure of the degree of genetic differentiation between samples

an example of intrinsic postmating isolation

the mule

mule

sterile offspring of a male donkey and a female horse

Two types of crows in Europe: known as the Corvus corone and Corvus cornix are examples of __________

extrinsic postzygotic isolation due to poorly adapted hybrids

extrinsic postzygotic isolation

isolated by external means

intrinsic postmating isolation

although these animals see each other in their environment a lot, they are not able to effectively mate and produce fertile offspring

ecological speciation

evolution of reproductive barriers due to adaptation to divergent environments

speciation genes

genes that cause reproductive isolation and hence speciation

Stickleback study freshwater vs salt water

freshwater stickleback lost their body armour due to the lack of large fish and the salt water sticklebacks kept their body armour because of the vast amounts of fish

hybridization

The exchange of genes between species as a result of occasional inter-specific mating

Polyploidy

An organism, tissue, or cell with more than two complete sets of homologous chromosomes

autopolyploidy

An individual that has more than two chromosome sets that are all derived from a single species

allopolyploidy

polyploidy resulting from contribution of chromosomes from two or more species (most common type that arises from occasional hybridization between species)

Evolutionary significance of polyploidy

1. Polyploids reproductively isolated from their diploid parents hence a form of sympatric speciation

2. Polyploids exhibit novel phenotypes allowing exploitation of new habitats

3. Hybrid vigour evident due to heterozygosity, particularly in allopolyploids

4. Approximately half of all flowering plants are of polyploid origin including many crops plants & invasive species

Jerry Coyne

"When we understand the origin of reproductive

isolating factors, we understand the origin of species"

Dolph Schluter

Study on sticklebacks

reproductive isolating mechanisms

pre-mating isolation, post mating isolation

types of premating isolation

Geographical, ecological, temporal, behavioural, mechanical, prevention of gamete fusion

types of postmating isolation

Inviability, sterility, or abnormal development of hybrids

F2 breakdown

Carolus Linnaeus

"father" of taxonomy, binomial nomenclature, he came up with the hierarchical system of classification: kingdoms, phyla, classes, order, family, genus, species

What is the purpose of a biological classification?

Name is key to the literature on an organism (predictive power)

Enables interpretation of origins and evolutionary history

taxon

a named taxonomic unit at any level (plural=taxa)

What are the levels for taxonomy

kingdoms, phylums, class, order, family, genus, species

taxonomy

theory and practice of classification

Systematics

study of biodiversity and the evolutionary relationships among organisms

Phenetics

Classifying species based solely on overall resemblance (largely dead)

Cladistics

Classifying species on the basis of their phylogenetic relationships

Schools of Taxonomy: Philosophical wars of the 70s and the 80s

Philosophical wars of the 70s and the 80s between the study of phenetics and cladistics

Willi Henning

Created the phylogenetic tree. Provided a depiction of the evolutionary relationships among groups of organisms.

phylogenetic tree

A family tree that shows the evolutionary relationships thought to exist among groups of organisms

Monophyletic Group

a single ancestor that gives rise to all species in that taxon and no species in any other taxon

Non-monophyletic group

a taxon whose members are derived from two or more ancestral forms not common to all members

Ancestral trait

a trait shared with a common ancestor

Derived trait

a trait that differs from the ancestral trait in a lineage

Homology

similarity of traits due to shared ancestry

Homoplasy

similarity of traits as a result of convergent evolution

Convergent Evolution

Evolution of structures that resemble one another and perform similar functional roles due to the shared ecology of unrelated organisms

Why is molecular biology relevant to evolution and phylogeny reconstruction?

1. All life is related through branching descent

2. Common genetic code is evidence that all life is related

3. Evolutionary relationships among species are reflected in their DNA and their proteins

Inferring species relationships from nucleotide sequences

1. Genes or parts of a gene can be sequenced for different species

2. Species can be assessed for changes in the sequence of nucleotides

3. These changes can be used to construct relationships in a branching diagram (phylogeny)

phylogeny

Evolutionary history of a species or group of species.

Wayne and David Maddison

Tree of life web project

provides 10,000 webpages about biodiversity and phylogenetic relationships

Key innovations for phylogenies

1. Origin of a novel trait resulting in adaptive radiation

2. Carriers of the trait can exploit new resources or sets of habitats

3. Usually associated with rapid evolutionary diversification (e.g. adaptive radiations)

Key points on the Nature Paper on Columbines

16 fold variation in nectar spur length among species

7 independent pollinator shifts - 2 from bee to bird; 5 from bird to hawkmoth

Clear directionality in spur length evolution with no evidence of reversal to shorter spurs

Pollinator shifts associated with speciation events due to premating isolation

The optimal mating rate is lower...

for females than males

Therefore females...

tend to resist most mating attempts by males

Males have evolved...

grasping structures to overcome resistance

Females also evolve...

behaviours to aid in resisting

This antagonistic coevolution

has the potential to escalate like an arms race

What does an arms race predict?

escalation of armaments over evolutionary time

nectar spur evolution

there was a rapid burst of speciation with acquisition of nectar spur

nectar spur

pouch for storing nectar

Biological Invasions

The successful establishment of a species in a region not previously occupied followed by rapid range expansion

Native

An indigenous species that occurs wild in a given region

Alien

A species that has been introduced to a part of the world to which it is not native

Also referred to as adventive, exotic or simply introduced species

Negative environmental consequences of biological invasions

1) Disrupt ecological processes in natural plant and animal communities

2) Displace species leading to their extinction

3) Adverse effects on human health

4) Serious economic and social impacts through reduction of yields

Invasive species in the USA

1) Economic cost = $120 billion per year

2) 50,000 introduced species, number rising

3) 42% of threatened and endangered species at risk primarily due to alien invasives

enemy release hypothesis

A hypothesis that states when a new animal or plant enters a new habitat, their population increases dramatically as a result of no threat of predation against them

Invasive species thrive in disturbed sites

the more disturbance the more vulnerable to invasion

Common attributes of successful invasive species

1) Rapid development to reproduction

2) Uniparental reproduction

3) High reproductive output

4) Well-developed dispersal mechanisms

5) Broad ecological tolerance

6) High phenotypic plasticity

phenotypic plasticity

ability of a genotype to alter its phenotype in response to environmental change - important trait in unpredictable environments

How do some plants evolve to protect themselves from humans?

Weeds will evolve to protect themselves from humans by trying to mimic what rice plants look like

The Problem with Pesticides

Pesticides have caused many bugs that eat plants to evolve rapidly and become resistant to pesticides

Zebra Mussels

an invasive species that has caused a lot of problems in Ontario specifically clogging up water intake pipes as well as damaging local fishing industries, the females can produce up to 30,000-1000000 eggs per season, free swimming larvae easily dispersed in water. They have also been linked to avian botulism

Purple Loosestrife

1)Plants competitive with high phenotypic plasticity, produce millions of small, easily dispersed seeds with high viability,

2)Populations genetically diverse due to multiple introductions, outbreeding, and polyploidy; provides opportunities for evolution of local adaptation

Purple Loosestrife Flowering Time

Flowering Time correlated with latitudinal gradient of seasonality//Flowers farther north have adapted to the short growing season

cline

a gradual change in trait means over a geographical transect

The world's worst aquatic invaders

1) Water hyacinth

2) Kariba Weed

What do the worst aquatic invaders have in common

Native to South America, introduced by humans to Old World tropics, free-floating with prolific clonal propagation, populations genetically uniform and invasiveness due to high phenotypic plasticity NOT genetic diversity

Herbicide control causes pollution of aquatic habitats so biological control methods are used

Management of invasive species

1) mechanical e.g. hand weeding, machines

2) chemical - herbicides

3) ecological e.g. burning, flooding • biological control

Biological Control of Invaders

The planned introduction of natural enemies (e.g. predators, parasites, pathogens) to control unwanted populations of invaders in alien range

Which species is easier to control: asexual or sexual?

asexual species have a limited amount of genetic diversity since the offspring are clones of whatever the parent species was. For species to be a good biological invader, they have to have phenotypic plasticity and phenotypic plasticity requires changes in genotypes. Asexual species take longer to experience change and are thus easier controlled

The amount of genetic diversity determines...

whether resistance evolves in plant invader

Clonal species have ________ diversity than sexual species

less

Advantages of Biological Control of invasive species

1) Non-toxic to humans; if conducted carefully no serious environmental impacts

2) If successful the effects are permanent

3) Economically cheap ($1 for biological control vs. $5 for chemical control)

What is the main danger of using biological control of invasive species

Sloppy science creates new invasion

crop mimicry

when weeds mimic crops to avoid being picked by humans when they go through their crops to see if they are weeds or not

E.O. Wilson

biodiversity, expert in myrmecology (study of ants), early founder of biodiversity science

What are the two most important global environmental problems?

1) Global warming & climate change

2) Loss of biodiversity

Global environmental problems

Global Warming and climate change

Loss of Biodiversity

Environmental Pollution

Human Famine

Spread of infectious diseases

Human Population Growth

How will organisms respond to climate change?

1)Migrate to more favourable environmental conditions (=ecology)

2)Adapt to changing environmental conditions (=evolution)

3)Go locally (or globally) extinct (=evolution)

Climate change alters ____

phenology