Lecture 10 Flashcards
1
Q
Characteristics of Cambrian Radiation-based on basic body plans
A
- 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 `
2
Q
Lobe fin fish
A
- 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
3
Q
Basal Vertebrates
A
- 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
4
Q
Invasion of Land
A
- 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.
5
Q
Ordovician
A
- 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)
6
Q
Silurian
A
- 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
7
Q
Vertebrate evolution leading to conquest of seas and land
A
- 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
8
Q
Selection For these things when invasion of land started
A
- resistance to gravity
- breathing air
- conserving water
- new methods of excretion
- extremes of cold and heat
- internal fertilization/protection of eggs
9
Q
Big players in invasion of land
A
- primitive vascular plants
- vertebrates
- insects
- spiders
10
Q
smaller roles in invasion of land
A
- snails
- annelids
- planarians
- onychophorans
11
Q
Devonian
A
- vascular plants diversify and grow larger
- myriaods
- primitive wingless insects
- scorpions
- primitive spiders
- first tetrpods
- by end, first forests of large trees
12
Q
Archaeopteris
A
- very large trees
- oldest petrified wood
- common around Henryville IN
13
Q
Development of gills
A
- 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
14
Q
First land animals
A
-Silurian: arthropods: primitive myriapods; mollusks: snails
15
Q
Some pre-adaptations
A
- 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
