M1: LEC 1: Speciation

define biodiversity.

the result of BOTH speciation (new species forming) and extinction (loss of species)

define speciation.

the process in which one species splits into two

Give an example of speciation.

1) one ancestor of Cichlids —> speciation —> more than 450 species of Cichlids in Lake Victoria

what is the morphological species concept?

the idea that “if the species look alike, then they are the same species” or species distinguished by physical traits (appearance)

what are the problems with the morphological species concept?

1) variation within species (ex: owls of different colors)

2) convergence evo.

covergence evo means different species may look similar due to similar adaptations

What are other ways to define species besides the morphological or biological species concept?

1) cryptic species: morphological similar, but genetically distinct

2) phenotypic plasticity: variations within species due to the environment

3) sexual dimorphism: male and female individuals of a species look different

Give an example of cryptic species.

The group of giraffes are morphologically similar, but are genetically different.

what is the biological species concept?

organisms can make offspring tgt, but cant make offspring with other types of groups or groups of interbreeding populations that are reproductively isolated

What are limitations to the biological species concepts?

does not apply easily to fossils, asexual organisms, or hybrids

define reproductive isolation.

biological diff. (physical or behavorial) reduces gene flow btwn groups of organisms

note: gene flow is possible by mating btwn groups

define reproductive isolating barriers.

biological characteristics reduces gene flow btwn groups of organism or a # of diff mechanisms that causes reproductive isolation

define prezygotic barriers.

barriers before fertilization —> prevents the formation of a hybrid offpspring

fertilization means the fusion of the sperm and egg

define postzygotic barriers.

barriers after fertilization —> the resulting zygote will face problems in the short-term or long-term

What are the types of prezygotic barriers?

geographic: pop. separated by a physical barrier

temporal: mate at diff times

ecological: mating occurs in diff eco. niches

behavioral: diff. mating behaviors

pollinators (a variation of eco. and behavorial): plants attract diff pollinators

mechanical: incompatible reproductive structures

gametic: egg and sperm do not fit tgt

Give an example of temporal isolation.

diff species of cicadas emerges once every # of years

Give an example of ecological isolation.

apple maggot flies mate on apples vs hawthorns

Give an example of behavioral isolation.

male frogs release diff pitches and female frogs prefer specific pitches

Give an example of pollinator isolation.

radial sym. monkey flowers attract bees while bilateral monkey flowers attract hummingbirds

Give an example of gametic isolation.

red sea urchin sperm does not fertilize purple sea urchin egg bc the egg has receptors alllowing successful fertilization of specific gametes

What are the types of postzygotic barriers?

extrinstic: hydrid offspring is unfit due to the environment

intrinstic: hydrid offspring is unfit due to genetic incompatibility

Give an example of extrinsic isolation.

orange/yellow blend butterflies + white/yellow blend butterflies = red/white butterflies are targeted more bc they do not contain the colors that indicate that they are poisonous

What are the two types of intrinsic barriers?

1) hybrid sterility (can’t make offspring)

2) hybrid inviability (can’t live too long)

Give an example of intrinsic isolation, specifically hybrid sterility.

horse + donkey = sterile mule (bc they have a mismatch of the # of their chromosomes)

What are the (3) geographic modes of speciation?

allopatric, parapatric, and sympatric

What are the two types of allopatric speciation?

1) vicariance - barrier splits the ancestral population into two

2) dispersal - few individuals colonizes a new region (called the founder’s effect)

define allopatric speciation.

pop.s are geographically separated, little to no gene flow

define parapatric speciation.

pop.s with some gene flow, experiencing diff selection pressures

give an example of parapatric speciation.

1) anthoxanthum on normal soil vs mine tailings (waste)

2) lizards living in white sand vs dark soil, but they can still mate with e/o

define sympatric speciation.

pop.s are in the same geographic area, lots of gene flow

Give an example of sympatric speciation.

two types of palm trees due to diff soil types leading to divergence in their pop.s

Why does sympatric speciation occurs rarely?

it has high gene flow

Rank the 3 geographic mode of speciation from highest gene flow to lowest gene flow.

sympatric, parapatric, and allopatric

What does the process of speciation look like?

co-exist + gene flow —> physical or ecological barriers —> over time, species start to differ —> total RI and genetic incompatibility is complete

Why is allopatric speciation the most common to occur?

1) It is easier to see how it occur.  It can occur w/o gene flow, so differences can easily arise within pop.s

2) The evidence (from the image) shows that immobile species tend to speciate while living on a small island.

What are other factors that causes speciation?

1) strong sexual selection

2) single event speciation:

a) polyploidy: hybrids w extra set of chromosomes than its parental species

b) hybrid: hybrids survives in a diff habitats than its parental species

Why does reproduction isolation arise from polypoidy speciation?

the difference in chromosome # leading to the gametes not being able to match w/ e/o