Lecture 10

Question 1

Characteristics of Cambrian Radiation-based on basic body plans

Answer 1

• rapid
• primitive members of still living phyla first appear
• few clades basal to two or more phyla
• high disparity, low diversity
• many short-lived lineages
• ancestral vertebrates present, but do not dominate ecology
• most animals are soft bodied but larger skeletonized animals evolve
• good portion of animals not adapted to live on land in this period so they had to change body plans and physiology based on selective pressures `

Question 2

Lobe fin fish

Answer 2

• have both gills and lungs
• thought they might have lived in places where oxygen levels were low in the air so they used gills to breathe sometimes and lungs to breathe other times
• fins and lungs are preadaptation to life on land

Question 3

Basal Vertebrates

Answer 3

• arise in Cambrian
• jawless fish ~20myr later in Ordovican
• fish with jaws first appear ~30myr after jawless fish in Silurian
• first tetrapods (vertebrates with legs) appear in Late Devonian, 100 my after end of Cambrian

Question 4

Invasion of Land

Answer 4

• major environment shift
• very demanding: selection for conserving water
• when you live in water there’s plenty but when you live on land you have to constantly carry this water around because biochemical reactions in your body rely on it to proceed.

Question 5

Ordovician

Answer 5

• plants move to live on land
• once plants get on ground, becomes much more attractive for animals to evolve to live on ground
• plants provide food for animals
• algeal near water, liverworts (non-vascular)

Question 6

Silurian

Answer 6

• conditions of the ocean before vertebrates have started going ashore
• first vascular plants
• coral reefs prevalent
• some major novelties: eurypterids appear–>giant scorpion-like, aquatic forms up to 9 feet long–>predators

Question 7

Vertebrate evolution leading to conquest of seas and land

Answer 7

• Agnatha: jawless vertebrates, poorly developed appendages
• evolution of paired appendages
• evolution of jaws
• advanced fish classes-placoderms, chondrichthyes (sharks), osteichthyes (bony fish), and sarcopterygians (lobe fin fish)
• lobe fins are ancestral the tetrapods (us), and they are the pioneers of vertebrate land life-evolution of lims. These fish have both gills and lungs

Question 8

Selection For these things when invasion of land started

Answer 8

• resistance to gravity
• breathing air
• conserving water
• new methods of excretion
• extremes of cold and heat
• internal fertilization/protection of eggs

Question 9

Big players in invasion of land

Answer 9

• primitive vascular plants
• vertebrates
• insects
• spiders

Question 10

smaller roles in invasion of land

Answer 10

• snails
• annelids
• planarians
• onychophorans

Question 11

Devonian

Answer 11

• vascular plants diversify and grow larger
• myriaods
• primitive wingless insects
• scorpions
• primitive spiders
• first tetrpods
• by end, first forests of large trees

Question 12

Archaeopteris

Answer 12

• very large trees
• oldest petrified wood
• common around Henryville IN

Question 13

Development of gills

Answer 13

• as fish got bigger, gills developed
• increases surface area but doesn’t take up much body space
• very effective means of transferring oxygen and carbon dioxide

Question 14

First land animals

Answer 14

-Silurian: arthropods: primitive myriapods; mollusks: snails

Question 15

Some pre-adaptations

Answer 15

• i.e. already have features that give some advantage in a new selective regime
• hard body coverings: prevent water loss
• effective means of propulsion (generally legs)
• internal fertilization
• Problems: gas exchange and excretion

Question 16

Gills of Fish

Answer 16

• allow them to get rid of toxic ammonia by directly excreting it
• no land animals can excrete just ammonia
• we use urea
• some animals are even better at disposing of ammonia and make uric acid which is insoluble (reptiles, birds) so it is much more water saving

Question 17

Plants moving to land and conducting photosynthesis

Answer 17

• current level of oxygen in air is 21% which has been pretty stable
• oxygen level spikes 300-250 mya and very strange creatures arise
• drops drastically to 16% which would be very difficult to breath
• all this happens because plants moved to land and made it habitable to us

Question 18

Methods of gas exchange

Answer 18

• oxygen in, carbon dioxide out
• integument
• gills
• lungs with alveoli
• trachea

Question 19

Kidney (in vertebrates) and Malpighian tubules (in insects)

Answer 19

• concentration of waste
• recovery of salt
• saves water
• responsible for modifying biochemistry to a less toxic nitrogen waste–>urea in amphibians, mammals and some reptiles

Question 20

Devonian-Permian

Answer 20

• land plants, first forests, massive photosynthesis
• C02 levels fall, organic carbon buried as coal, O2 rises
• vertebrates can come to land and first land-laid egg
• age of giant insects

Question 21

Insects

Answer 21

• crucial players on land
• have primitive arthropod ancestor in common with crustaceans, millipedes and centipedes and chelicerates (spiders)
• most diverse arthropods and seem to have evolved on land

Question 22

Insect relationships

Answer 22

-Apterygota (silverfish), Paleoptera (dragonflies) and neoptera (butterflies and house flies and bees) all have a common ancestor

Question 23

Origin of insects

Answer 23

• had an aquatic ancestor that moved to land
• required a transformation of aquatic leg to a terrestrial one and a new means of breathing
• marine ancestor likely had gills on legs
• ancient insects: trachea on land as adult, gills on aquatic larvae
• very first insects were wingless

Question 24

Origins of wings

Answer 24

-apparently evolved from wing-like gills of aquatic insect larvae

Question 25

Crustacean and Trilobite limbs

Answer 25

- biramous limb | - trilobite had filamentons branch

Question 26

Insect limb

Answer 26

-uniramons limb

Question 27

Evolutionary trends in early insect evolution

Answer 27

- wingless - loss of exopodite of aquatic ancestors, evolution of trachea - legs on all segments: lost on abdomen but converted to mouth parts on head - reach very large sizes because of high oxygen levels and no competition from flying vertebrates

Question 28

Why were vertebrates good on land?

Answer 28

- nerve cord (dorsal) - vertebral column (built around notochord) - circulatory cord/system (ventral heart) - segmentation - paired appendages - somites=paired groups of body wall muscles - hydroxy apatite (bone) skeleton

Question 29

Vertebral column

Answer 29

- provides different function for swimming fish than for walking tetrapods - allows fish to swim like they do - tail fin swims side to side which is controlled by muscles along the body wall that are tied to the skeleton - skeleton doesn't have to support the weight of walking

Question 30

fish lungs

Answer 30

- retained in tetrapods | - converted to swim bladders in teleosts

Question 31

Amphibians

Answer 31

- gas exchange via skin and lungs-not water tight - major steps and preadaptations: lungs (preadaptation), legs (from lobe fin), vertebral column (support of body on land)

Question 32

Eusthenopteron, Ichthyostega, and advanced Labrinthodont

Answer 32

-look at this page

Question 33

Amphibian reproduction

Answer 33

- aquatic egg, development of fish-like tadpole - gills - ammonia excretion - swims with tail - metamorphosis from tadpole to frog

Question 34

Origin of reptiles

Answer 34

- carboniferous - skeletons of first reptiles very similar to amphibians - amazing novel evolutionary event-->new mode of development - freed themselves from dependence on water-->lay eggs or have live births, invent internal fertilization

Question 35

Revolution in conquest of land by vertebrates

Answer 35

- water tight skin - better limbs - better sense organs - free from return to water for reproduction - amniotic egg (look at drawing)

Question 36

What's an egg?

Answer 36

- yolk sac: has nutrients - waste sac called _____ - amniotic cavity: where embryo develops