Lecture 6: Life beneath the Palaeozoic ocean wave

Question 1

As we’ve moved into the Proterozoic?

Answer 1

communities become more structured (things are starting to live in different places and eating in different ways).
more ecological interactions

Question 2

Pelagic organisms (live in the water column):

Can be divided into…

Answer 2

planktonic -drifters/floaters

nektonic - active swimmers

Question 3

Benthic (or benthonic) organisms, the bottom dwellers:

Can be divided into…

Answer 3

Epifaunal- live ON sediment surface and can be…

• sessile/ anchored
• mobile

Infaunal- live IN the sediment

Question 4

What are Trilobites?

Answer 4

Three lobed…

• head
• body
• tail

Mainly Benthic…

Question 5

Arthropods

Among first to…

Answer 5

Develop vision
Sensitive to motion (prey)
some had stereoscopic vision (distance away)

rigid crystalline calcite lenses
good depth of focus and corrected spherical aberration

schizochroal eyes – fewer lenses

development of camouflage/ colour patterning

…accelerated evolution?

Question 6

Arthropods

Answer 6

soft tissues
legs gill and antennae
roll up for protection- jointed

Question 7

The first (Cambrian) reefs

Answer 7

Sponges made of calcium carbonate.
appear ~525 Ma
became extinct by end of the Cambrian

Question 8

Corals arrive

Phylum Cnidaria

Answer 8

jellyfish, sea anenomes, corals
Cup shaped with tenticles
Benthic
Sessile
Much folded gut wall – increases digestive ability

Question 9

Echinoderms

Answer 9

sea urchins, starfish
major components of reefs
disarticulate after death: produce crinoidal limestones

Question 10

Brachiopods (Lamp shells)

Answer 10

all benthic (lowest point in water)
sessile filter
anchored by ‘stalk’
feeders (‘sit and suck’)

Question 11

Molluscs

Answer 11

‘soft tissue’
Class Cephalopoda- most common (‘head foot’)
chambers: regulate buoyancy

Question 12

First cephalopods were…

Answer 12

nautiloids (simple chambers)
had straight shells- cumbersome, buoyancy regulation difficult
‘orthocones’

Question 13

Winding you up through the paleozoic…

Answer 13

Nautiloids into goniatites- had more and more coiled shells
Easier to move around (better buoyancy regulation)
More complex internal divisions

Question 14

Written in stone

graptolites

Answer 14

resistant organic colonies (collagen)
filter feeders
earliest were sessile
later ones planktonic- didn’t have to attach

Question 15

Palaeozoic plankton

Answer 15

as they evolve they reduce no. of branches (‘stipes’)
many 4
Ordovician: two stipes (“tuning fork graptolites”)
Silurian: one stipe (monograptids)
first macroscopic plankton

Question 16

High ocean drifters

Answer 16

graptolite facies: defined association / environment
black shales
deep water, low O2
no benthos, preserved laminations, pyritic (FeS2)
dead graptolites drift through water column undisturbed

Question 17

Biological organisms are classified using

Answer 17

a hierarchical system

Question 18

Highest level of classification is into 3 domains:

Answer 18

Archaea, Eubacteria, Eukaryota

Question 19

The Eukaryota is divided into 4 kingdoms:

Answer 19

Protista, Fungi, Plantae, Animalia

Question 20

Classification system

Answer 20

Kingdom
Phylum
Class 
Order
Family
Genus 
Species

Question 21

Lower levels of classification include…

Answer 21

the genus and species
these use “Linnean binomials” (i.e., two names)

NOTE: species names are italicised when typed (if you write them by hand they should be underlined: Homo sapiens)

NOTE also that family, order, class, phylum names are NOT italicised, nor are informal names, such as ‘hominids’

Question 22

Biostratigraphy: 1

environmentally controlled fossils can be used…

Answer 22

To trace similar environmental conditions through time

but these are no good for dating sediments.

Question 23

Biostratigraphy: 2

What properties make a a fossil useful for dating rocks?

Answer 23

rapid evolution/extinction
abundance
distinctive, easily identified
facies independence
mostly pelagic (or pelagic larval stages)
e.g., Silurian graptolite biostratigraphy

Question 24

Benthic (or benthonic) organisms, the bottom dwellers:

Infaunal

Answer 24

Live IN soft sediment (burrowers), or bore INTO hard substrates

Question 25

Something that lives within the water column is referred to as…?

Answer 25

Pelagic

Question 26

Something that lives in the bottom of the water is referred to as…?

Answer 26

Benthic

Question 27

How do arthropods grow?

Answer 27

By moulting their exoskeleton

Question 28

What were reefs in the precambrian like?

Answer 28

Reef systems made out of stromatolites.

These started to get eaten away by the browsers and grazers as we move into the Cambrian.

Question 29

Benthic meaning

Answer 29

Something that lives in the bottom of the water

Question 30

Sessile meaning

Answer 30

Anchored to ground

Question 31

Planktonic

Answer 31

drifters/floaters

Question 32

Nektonic

Answer 32

active swimmers