Lecture 20

Question 1

Plato

Answer 1

• thought that true knowledge wasn’t present on our planet but in a transcendental plane of ideas
• true knowledge comes from the knowledge of the Idea
• the world of ideas is populated with types which are discrete, immutable and ideal representations of things that exist

Question 2

Aristotle

Answer 2

• thought we learn about truth from this planet
• thought true knowledge was empirical comes from real world=essentialism
• organisms have essential features they have a predisposition to produce organisms of its kind

Question 3

Ladder Thinking (Similar to Neoplatonists “Great Chain of Being”)

Answer 3

• wrong idea
• first hit on Google
• inevitable progression toward complexity-species destined to become more complex
• can see the other species in the ladder still living together today: weird because there must be several life origins to be able to see the monkey that is thought to have evolved into another species
• no extant species transform into another extant species (i.e. chips transform into the human with time)

Question 4

Relatedness

Answer 4

• defined in time since most recent common ancestor
• has nothing to do with alleles
• genetic similarity is just a byproduct of relatedness; it’s not how you define relatedness

Question 5

Ideas that Darwin proposed matched Linneasus’ classification

Answer 5

• not a coincidence
• it’s how life evolved
• speciation events happen at teh nodes

Question 6

Phylogenetic Species Concept

Answer 6

• works with sexual and asexual organisms
• emphasizes phylogenetic history of a group
• a species is an irreducible cluster of individuals that is diagnosably distinct from other clusters, and within which there is a parental pattern of ancestry and descent
• so species A is defined by the specific alleles its individuals have at different loci and individuals from species B would have different alleles

Question 7

To have reduction in gene flow need isolating barriers

Answer 7

• can happen premating or postmating
• can happen prezygotic or postzygotic
• premating is prezygotic by definition

Question 8

Premating

Answer 8

• means they don’t mate

- can be sexual or environmental in nature

Question 9

True or False: pair of siblings more genetically similar than a pair of cousins, therefore siblings are more closely related

Answer 9

• false

- relatedness is defined in time since most recent common ancestor

Question 10

Tree Thinking

Answer 10

• NO SUCH THING AS EXTANT SPECIES BEING MORE OR LESS EVOLVED/BASAL THAN ANOTHER EXTANT SPECIES
• all extinct species can be more basal

Question 11

Linneaus’ and Common Descent

Answer 11

• linnaeus system was proposed way before idea of common descent appeared in Darwin’s book
• Linnaeus was not thinking about common descent, but he observed that animals could be classified in a hierarchical way
• look at graphic and be able to reproduce and compare to tree

Question 12

Species and Speciation

Answer 12

• speciation happens at nodes on a tree diagram

- the definition of species is a convention, sometimes it works well and sometimes it doesn’t.

Question 13

Typological or Essentialist Species Concept

Answer 13

• a speices has a set of recognizable essential characteristics that define it
• we can choose an individual that we believe is “representative” of that species and we call it the species “type”
• but how do you choose the type?

Question 14

Biological Species Concept (BSC)

Answer 14

• considers that a species is a group of populations that is evolving independently of other species
• “species are groups of actually or potentially interbreeding populations, which are reproductively isolated from other such groups”
• gene flow is reduced but may exist at low levels between two different species (100% reproductive isolation not required)
• means that hybrids may be formed and may be viable/fertile, but would still have 2 species
• doesn’t work with bacteria because of asexual nature

Question 15

Gene Flow

Answer 15

• movement of alleles from one population to another
• individuals migrate from one population to another and reproduce
• pollen and seeds can be carried by wind/pollinators

Question 16

Reproductive Isolation

Answer 16

-reduction or prevention of gene flow between populations because of genetic differences between them

Question 17

Premating Isolation: Ecological Isolation

Answer 17

• prezygotic
• two kinds of crickets that are very similar in habitat, morphological and calling songs
• don’t mate because adults aren’t alive at same time of year during their life cycles

Question 18

Premating Isolation: Sexual isolation

Answer 18

-prezygotic
-lacewings: one sex does not respond to others display signal
or
-flowers of the same species but one is fertilized by bees and the other by hummingbirds. The animals won’t visit the other flower in the species so the flowers don’t mate

Question 19

Postmating Isolation: Gametic Isolation

Answer 19

• prezygotic
• sea urchins: gametes fail to unite because proteins on surfaces of sperm and egg cells from different species do not bind

Question 20

Postzygotic Isolation

Answer 20

• intrinsic: does not depend on context
• i.e. hybrid inviability
• extrinsic: depends on context
• i.e. ecological inviability and behavioral sterility

Question 21

Ecological Inviability

Answer 21

-hybrids lack a niche where they can be competitive against their parents

Question 22

Behavioral Sterility

Answer 22

-parents around hybrids are better at obtaining mates than hybrids

Question 23

Hybrid Inviability

Answer 23

-usually during embry development

Question 24

Hybrid Sterility

Answer 24

-gametes are not viable