BIOL 1010 chapter 19 restart

What evidence was used to hypothesize chordate evolution and why?

• Anatomical (structure)

• Molecular (DNA)

• Fossils

• This evidence reveals shared derived characteristics and evolutionary relationships.

What was the first clade of chordates to branch off?

Lancelets

What’s the purpose of a notochord?

Provides some skeletal support in vertebrates and is the main support in invertebrates

What are distinguishing features of vertebrates?

• Spinal column

• Skull

• Endoskeleton

What’s the endoskeleton made of?

Cartilage, bone or both

How did the evolution of jaws allow life on land? 

Allowed for diverse feeding strategies

How did the evolution of lungs and lung derivatives allow life on land?

Enabled respiration

How did the evolution of lobed fins allow life on land?

Allowed movement and weight-bearing due to strong skeletal support

What were the first vertebrates to colonize land?

Tetrapods

What did tetrapods adapt to for a fully land-based lifestyle?

Amniotes

What provides the main support for hagfish and lampreys? Why?

Notochord because their vertebrae is made of cartilage prongs (so not strong enough to support body)

What kind of protection does the nerve cord have in hagfish and lampreys?

Hagfish have no protection and lampreys have little protection

Where do hagfish live?

Dark and cold seafloor

What are 5 characteristics of hagfish?

1. Nearly blind

2. Great sense of smell and touch

3. Slime glands

4. Tooth structure on tongue

5. Tie their bodies into knots

What do hagfish eat and how do they eat it?

They eat dead/dying vertebrates by entering the carcass.

What do hagfish do when threatened?

Release slime onto predator that clogs their gills and mouth, suffocating it. Then they tie themselves into a knot to remove the slime from their bodies.

What do humans use hagfish for?

Harvested for their meat and skin that’s processed into faux-leather

Where do lampreys live?

Buried in sediment of freshwater streams

Where do adult lampreys migrate?

Seas or lakes

What do lampreys eat and how do they eat?

They act as parasites that attach onto fish. They use their tongue to pierce skin and eat blood and tissue.

What is done to prevent the spread of lampreys into Great Lakes?

Chemicals (lampricides) are put into the freshwater streams to kill them

When did jawed vertebrates appear in the fossil record?

440 million years ago in the mid-Ordovician period

How do paired fins and tails contribute to evolutionary success of jawed vertebrates?

Allow for efficient swimming and maneuvering

How do jaws contribute to evolutionary success of jawed vertebrates?

Allows wider range of feeding strategies

What’s the basic jaw structure?

2 skeletal rods connected by a hange

What was the original purpose of gill slits and what is it’s current function?

Original function was to filter feedings but evolved to gas exchange.

What are the 3 lineages of jawed fishes?

• Chondrichthyes

• Ray-finned fishes

• Lobe-finned fishes

What species are included in chondrichthyes?

Sharks and rays

What is the skeleton of chondrichthyans made of?

Cartilage

What do sharks eat?

Fish and marine animals

Why are sharks well suited to their diet?

They have streamlined bodies (ability to move smoothly), powerful jaws, sharp teeth and high senses

What are 7 characteristics of sharks?

1. cartilaginous skeletons

2. streamlined bodies

3. rows of teeth

4. lateral line systems

5. electroreceptors

6. high senes

7. swim continuously

What’s the purpose of the lateral line system?

detects vibrations and changes of pressure in the water which helps locate prey, avoid predators and navigate their surrounding.

where do rays live?

on the ocean floor and bury themselves in sand

how big can rays get?

large species like manta rays can get up to 6 meters (19 feet) wide

what’s the body structure of a ray?

flattened, dorsoventrally compressed bodies with eyes on top of their head and broad pectoral fins that are fused to the body

why is it easy to step on a ray when swimming/diving?

they’re usually buried in sand so you can’t see them

why is it potentially dangerous to step on rays?

some rays (stingrays) have venomous spines on their tails that can cause pain or even death

what’s the purpose of the fin extensions in front of the mouth of rays?

they help funnel water and plankton into the mouth during suspension feedings

what species are included in ray-finned fishes?

tuna, trout, goldfish, seahorses, balloon fish and flounders (all bony fishes)

what is the skeleton of ray-finned fish made of?

they have bony skeletons reinforced with calcium phosphate

what is the basic body structure of ray-finned fish?

their fins are supported by thin, flexible rays and they’re covered in flattened scales

what’s the purpose of the mucous secreted by ray-finned fish?

reduces drag and allows for faster/smoother swimming

what’s the purpose of the operculum?

it covers and protects the gills to allow the fish to breathe when still, by moving water over the gills

what did swim bladders evolve from?

ancient lungs that early fish used for breathing in oxygen-poor shallow water

what features give ray-finned fish success (4)?

1. lightweight and flexible fins for moving

2. bony skeletons for support

3. swim bladders for buoyancy

4. diverse adaptations to thrive in different habitats

where do ray-finned fish live?

every aquatic environment on Earth

how does the balloon fish protect itself from predators?

inflates its body and raises spines

how does the seahorse go through reproduction?

when the female deposits its eggs into the male’s brood pouch where he fertilizes and carries them until they hatch

how does the flounder camouflage?

uses pigment cells in its skin to match the colour and texture of the seabed

how do flounders and other flat-fish develop to have eyes on top of their head?

during development, one eye migrates from one side of the head to the other so both eyes end up on the upper side of the body

what are some characteristics of lobe-finned fish?

they have muscular fins supported by rod-shaped bones

where do lobe-finned fish live?

coastal wetlands

how do lobe-finned fish move underwater?

they use their fins to walk

what are the 3 lineages of lobe-fins that survived to now?

1. coelacanths

2. lungfish

3. tetrapods

what groups of vertebrates are the descendants of the earliest land-dwellers?

amphibians, reptiles and mammals (all tetrapods)

what obstacles did vertebrates face on land that they had to adapt to?

they had challenges in gas exchange, water conservation, structural support, reproduction and locomotion

what evidence suggested that lobe-finned fish were the immediate ancestors to tetrapods?

they had fleshy paired fins with bones homologous to tetrapod limbs. they also had lungs capable of getting oxygen from the air

what hypothesis regarding lobe-finned fish’s move to land did Alfred Romer make?

they use their limb-like fins and lungs to move between shrinking pools during times of drought. the ones that were best able to move, survived and reproduced leading to adaptations for terrestrial life.

what are Eusthenopteron?

a fully aquatic lobe-finned fish that showed features leading to tetrapods

what are Ichthyostega?

an advanced tetrapod with limbs, neck, and shoulders that could do terrestrial locomotion but was still fishlike

what were the differences between Ichthyostega and water-dwelling organisms?

Ichthyostega had limbs with digits, shoulder and a neck. Aquatic ancestors (Eusthenopteron) had gill-based respiration, no neck and used fins