4- Taxonomy and phylogeny

Question 1

what is taxonomy

Answer 1

the science of naming, defining and classifying groups of biological organisms

Question 2

how do taxonomy and phylogeny relate

Answer 2

classification of a species reflects the phylogeny

Question 3

how does classification of extant and extinct species compare

Answer 3

classifying living species is relatively simple but classification of fossils is more complex/difficult

Question 4

how did phylogenetic analysis work in the “BAD OLD DAYS”

Answer 4

• both the presence and absence of characters considered
• Evolutionary relationships not achieved through rigorous scientific analysis ( hunches)
• different experts would disagree on importance of characters
• used to classify via stratification of fossils , now known fossil record is patchy n biased
• lasted till 1980s

Question 5

How did the cladistic revolution come about

Answer 5

fierce debates through the 70’s and 80’s over whether it would work, eventually everyone was convinced

Question 6

How does cladistics work

Answer 6

1) Creation of a character matrix, focusing on presence of characters not absence (they can be lost)
2) Analyse character distribution with parsimony or Bayesian methods
3) Identify homologous/analogous characters and hence synapomorphies, synplesiomorphies, automorphies to eliminate homoplasy
4) establish sister groups rather then ancestor-descendant relationship
5) illustrate using a cladogram (triangular or square)

Question 7

synapomorphoes

Answer 7

A synapomorphy is a shared apomorphy (clade distinguishing feature) that distinguishes a clade from other organisms and originated from the last common ancestor

Question 8

synplesiomorphies

Answer 8

A trait shared by two or more taxa

Question 9

automorphies

Answer 9

autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon.

Question 10

Why was cladistics controversial

Answer 10

classification became difficult with sister groups and some groups fell out of favour and needed redefining into a cladistic hierarchy

Question 11

in cladistics what type of group do u want

Answer 11

monophylectic = all have a common ancestor `
- don’t want a paraphylectic (group that shares a common ancestor with another group) or polyphylectic group (more then one ancestor)

Question 12

How does the total group . crown group and stem group work in cladistics

Answer 12

Total group = everything , extinct or living
Crown = all living and some fossils that fall out inbetween
Stem = no living representatives

• any fossils that fall in the crown group have the same characters as the living crown group organisms
• anything in the stem group does not have same characters (or some) as the living organisms (inflates phylogeny)
• helps to work out when characters evolved
• simple but complicated by language issues

Question 13

Case study : dinosaur relationship

how were dinosaurs initially classified

Answer 13

• seen as not a natural group
• thought they evolved from theodonts
• pre cladistic analysis

Question 14

how did cladistics analyse dinosaurs

Answer 14

• cladistic analysis found reptiles to be primarily characterised by their skulls
• discovered pterosaurs were a sister group to other dinos
• saurischian and ornithischia are a monophylectic group
• crocodiles are much more basal

Question 15

what are the ornithischia

Answer 15

armoured , horned and duckbilled dinosaurs

Question 16

(ornithischia) - features of stegosaurs

Answer 16

• 12 species (not very diverse group)
• 300-1500 kg with thick legs
• feed on plants with beak, huge guts to break down veg slowly
• very slow moving 6-7 km/h , their size protects them
• brain 0.001% of body mass
• defining character = spines on back for protection , plates came later + basal groups have more spines

Question 17

(ornithischia) - Ankylosaurs

Answer 17

• 30 species , middle Jurassic - late cretaceous
• armour plated with large spines on back + head
• ossified skin used for protection
• large bones in strong tail
• up to 3500 kg
• slow 10km/h
• brain only slightly bigger then stego

Question 18

(ornithischia) - pachycephalosauria

Answer 18

• 16 species
• head butters, had a bipedal stance
• longer tail for balance
• confined to cretaceous
• last of the groups to evolve
• 2-8m long, 450 kg
• hung about in herds
• very quick , lighter +more agile. all adaptation to evade predators +avg brainsize

Question 19

(ornithischia) - ceroptopsia

Answer 19

• 40 species , Jurassic -> cretaceous
• large but surprisingly agile
• 1m-9m, 25-7000kg, 2-4 km/h
• charge quite quickly (method of protection) 35 km/h
• herds and avg brain size
• characterised by frill at back of the skull , v ornate + elaborate with 2 big horns

Question 20

(ornithischia) - Ornithopods

Answer 20

• 100 species , divided into 3 groups
• classic herbivores , bipedal with long tail , v variable in size 1-15m
• early Jurassic -> cretaceous
• large ones can be up to 23,000kg
• herds , speed vary greatly 60 km/h (small ones) to 15/20 km/h
• relatively intelligent

Question 21

(ornithischia) features of hadrosauridae (sub-group of Ornithopods )

Answer 21

• duck billed dinosaurs
• elaborate structures on head due to sexual dimorphism
• intelligent animals , could make noise and communicate via structures on head
• live in herds

Question 22

what are the two groups of saurischia

Answer 22

1) sauropods

2) theropods

Question 23

(saurischia) features of sauropods

Answer 23

• 150 species , triassic -> end cretaceous
• different hip bone
• earliest found are bipedal then moved to quadrupedal, neck and tail elongated achieving gigantism
• 15 m tall on back legs , 40m head to tail
• 75,000 kg (no need for defence)
• tiny heads = low intelligence
• 20 yrs to maturity , lifespan about 100 yrs

Question 24

(saurischia) what are segrosauria

Answer 24

enigman tend to ignore them

Question 25

(saurischia) featurs of theropods

Answer 25

• 160 species
• carnivores, same basic bipedal body plan
• powerful back legs + reduced front legs
• tail for balance, huge jaws + teeth (v varied in size)
• incredibly intelligent , active hunters with big eyes
• developed senses
• small forms v quick

Question 26

Are birds really dinosaurs

Answer 26

• coelurosaurie in the theropods is where bird line characteristics started to develop, theropods get small + inc brain to body size ratio
• cladistics show birds are a monophylectic group
• feathers/scales = integumentary structures are all homologous (dev for diff functions)
• phylogenetically birds must be dinos