Lecture 5: Traits used for classification

Question 1

How are traits used in classification

Answer 1

to compare organisms

Question 2

Morphological traits (shapes of the body)

Answer 2

• Overall bodily shape such as ‘having four legs’
• Tissues, such as bones and branches
• Individual cells, especially for unicellular organisms
• Organelles such as the nucleus and chloroplast (photosynthesis)

Question 3

Biochemical traits

Answer 3

Presence and absence of metabolic pathways etc.

Question 4

Genetic traits

Answer 4

• Presence and absence of related genes
• Differences in those genes

Question 5

In general, organisms which share similar traits are ___

Answer 5

likely to be evolutionary related to one another

Question 6

What trait is used a lot for classification?

Answer 6

• Skull morphology is used a lot for classification due to its complexity
• It is less likely for complicated traits to evolve independently in unrelated organisms and end-up looking near-identical by chance

Question 7

Similar morphology does not always mean

Answer 7

close relatedness

Question 8

Australian mole and North American mole look very similar however __

Answer 8

• Australian mole is marsupial
• North American mole is placental
• Evolved under selective pressure for their ground-burrowing lifestyle
• These species are not closely related at all
• Diverged~140-160 million years ago
  ancestral mammal

Question 9

Convergent evolution

Answer 9

Unrelated lineages of organisms can develop similar-looking traits independently

Question 10

Homology

Answer 10

similar traits in organisms shared through common ancestry

Question 11

All mammals feed infants with ___ implying ___

Answer 11

milk
* This suggests that the ancestral mammal already had the milk-feeding trait which got passed to all members of its lineages

Question 12

_____ is said to be a homologous trait

Answer 12

‘Feeding milk’

Question 13

Analogy

Answer 13

similar-looking trait in organisms which occurred not by shared ancestry

Question 14

Mole-like trait is not seen in all mammals meaning

Answer 14

• Ancestral mammal probably did not have mole-like traits
• Mole-like traits developed independently in Australian and Placental moles lineages, and ended up looking alike

Question 15

The mole-like trait is ___

Answer 15

analogous

Question 16

Shared ancestral character

Answer 16

trait held by the common ancestor which got passed on to all* descendants

Question 17

___ is a shared ancestral character for all mammals

Answer 17

‘Feeding milk’

Question 18

Shared derived character

Answer 18

a unique character found in a lineage which developed after the common ancestor diverged

Question 19

‘Bag for infants’ __

Answer 19

is a homologous trait for marsupials

Question 20

_____ is a shared derived character, unique to marsupials

Answer 20

‘Bag for infants’

Question 21

Shared ancestral/derived characters are ___ terminologies

Answer 21

relative
* It changes depending on who you set as the common ancestor

Question 22

If you choose the common ancestor of all mammals as the reference, “bag for infants” is a ____ trait

Answer 22

‘Bag for infants’ is a shared derived character unique to marsupials

Question 23

If you choose the common ancestor of marsupials as the reference, “bag for infants” is a ____ trait

Answer 23

‘Bag for infants’ is a shared ancestral character

Question 24

The ‘milk-feeding’ trait of mammals becomes a ____ in reference to all vertebrates

Answer 24

shared derived character

Question 25

'Having a backbone' is a __ if you are referring to Vertebrae

Answer 25

shared ancestral character

Question 26

The ancestral chordate is a __ in the tree of life

Answer 26

local, shared-derived trait

Question 27

Different lineages of marine mammals

Answer 27

* Dolphins and Whales * Seals * Manatees * These traits are shared derived characters in relation to entire mammals

Question 28

Are Marine lineages homologous or analogous?

Answer 28

These traits are analogous to each other since they were acquired independently in their lineages

Question 29

Very complicated traits are __ in multiple independent lineages by convergent evolution

Answer 29

unlikely to emerge

Question 30

Example of homologous structure in humans and birds

Answer 30

* 'Forelegs' of humans and birds share clear similarities * Very low chance for these structures to match to this extent if they have evolved independently * Forelegs of humans and birds are homologous (shared ancestry)

Question 31

Differences in structure between bats and birds

Answer 31

* Birds have reduced digits (Metacarpals/Phalanges) with feathers attached to the forelimb * Bats have elongated digits which sustains a membrane, like an umbrella

Question 32

Are the wings of bats and birds homologous or analogous?

Answer 32

* Wings of birds and bats are analogues * The ancestral 'foreleg' structure evolved independently in two different lineages to give rise to a flying mechanism * This ended up giving rise to 'somewhat- similar' morphologies

Question 33

Similarities and differences in structures give hints to

Answer 33

evolutionary relatedness of organisms

Question 34

___ does not always correspond to evolutionary distance

Answer 34

Different morphology

Question 35

Small change in a ___ can lead to huge diversity in ____

Answer 35

gene (genotype) morphology (phenotype)

Question 36

____ are used in combination to deduce phylogeny

Answer 36

Morphologies and genes

Question 37

Taxonomy using molecular genetics

Answer 37

* Any organism contains multiple genes in their genome * Different organisms frequently have related genes which they acquired through shared ancestry: homologous genes * Homologous genes can be used to deduce evolutionary relationship between organisms based on how similar/different their sequences are

Question 38

Orthologous genes

Answer 38

* A common ancestor diverges into two species * Both species inherits the same genes from their ancestor (homologous genes with shared ancestry) * Since they are in a different lineage, the homologous genes can now begin to evolve (mutate) differently

Question 39

Ex of Ortholgous genes

Answer 39

* Example: common ancestor speciates into Humans and Chimpanzees * Both species inherit 'Gene_A Ancestor' * Overtime, the ancestral gene evolves into: * 'Gene_A Human' in Humans * 'Gene_A Chimps' in Chimpanzees

Question 40

Paralogous genes

Answer 40

A gene makes a copy of itself within the same species * The two copies of genes (in the same species) can begin to evolve differently

Question 41

Can evolutionary relationships be deduced when looking at paralogous genes in a gin organism?

Answer 41

You can not deduce evolutionary relationship between species if you are only observing paralogous genes within the same organism

Question 42

Typically, genes with important functions __

Answer 42

evolve slowly * Higher chance for a mutation to be detrimental to the organism * Lower frequency of accumulating mutations

Question 43

Ex of genes that evolve slowly

Answer 43

The 16S and 18S ribosomal RNA genes, used for translating mRNA into proteins, evolve especially slowly and are the gold- standards for molecular phylogeny

Question 44

Use faster-evolving genes to analyze

Answer 44

more-recent evolutionary events Slower-mutating genes may not accumulate mutations quickly enough to observe recent evolutionary events

Question 45

Use slower-evolving genes to compare evolution

Answer 45

over longer period of time Faster-evolving genes accumulate too many mutations for a long-term comparison