11. The rise of tetrapods

Life on land provided what?

Opportunites for early animal colonists

• Higher O2 and new resources of food allowed for animals to thrive

Green Algae Characteristics & Terrestrial organism

• Anchoring Structure - derived (roots)

• Support Structure - Derived (stems)

• Internal transport - Derived (vascular systems)

• Muscle/nerve cells - N/A

• Protection against desiccation - derived (cuticle)

• Gas exchange - derived (stomata)

• Terrestial Organism - Plants

Marine Crustaceans Characteristics & Terrestial Organism

• Anchoring Structure - N/A

• Support Structure - Ancestral

• Internal transport - Ancestral

• Muscle/nerve cells - Ancestral

• Protection against desiccation - Ancestral

• Gas exchange - Derived (tracheal system)

• Terrestial Organism - Insects

Aquatic lobe-fin Characteristics & Terrestial Organism

• Anchoring Structure - N/A

• Support Structure - Ancestral (Skeletal system) & Derived (limbs)

• Internal transport - Ancestral

• Muscle/nerve cells - Ancestral

• Protection against desiccation - derived (Amniotic egg/scales)

• Gas exchange - Ancestral

• Terrestial Organism - Terrestrial vertebrates

what challenges where there on land?

1. Scarec water

2. Temperature Fluctuations

3. No support against gravity

What were the first animals to colonize land?

The arthropods

• about 450mya

  • Millipedes, centipedes, spiders and wingless insects by 410mya

  • Vertebrates by 365mya

Characteristics of arthropods

They have appendages for walking, feeding, sensory reception, reproducion and defense

• Their appendages are jointed and come in pairs

  • Athropods body are completely covered in a cuticle (exoskeleton) which is built from layers of protein and chitin

    • this helped them colonize land

Aquatic arthropods

they have gills for gas exchange

Terrestial arthropods

they have specialized gas exchange structures

• e.g. insects have tracheal systems w/ branched air ducts

How old does the oldest insect fossils date back to?

~415 mya, Devonian

When did the explosion of insect diversity occur?

Carboniferous and Permian periods

Flight in insects

Flight has helped insect excape predators, find food, mates, and disperse to new habitats

• Usually done by the use of wings

  • wings are extensions of the cuticle, so insect do not have to sacrifice walking legs for flight

Lepidopterans

includes moths and butterflies

• these undergo complete metamorphisis

  • the larval stage, a caterpillar, is specialized for eating and growing

    • these resembles bird dropping so they do not get eaten

  • The adult stage is specialized for dispersal and reproduction

Hymenopterans

includes ants, bees, and wasps

• They undergo complete metamorphosis and are highly social insects

Hemipterans

includes stink bugs, bed bugs, and so-called other tru bugs

• they have piercing mouthparts and undergo complete metamorphosis

  • the young resemble the adults just smaller and lack wings

What kinds of fish occured during to the DEVONIAN

Lobefins fishes

• they lived in the coastal wetlands

  • in one lineage the fins became prograssively more limb-like while the rest of the body retained adaptations for aquatic life

    • e.g. tiktaalik provides new insights into early tetrepod evolution

3 Clades of amphibians

1. Clade Urodela - Salamanders

2. Clade Anura - Frogs and toads

3. Clade Apoda - Caecilians

Caecilians - Apodans

The caecilians are legless and resemble worms

• however they have a backbone

  • they inhabit moist soils in tropical habitats

  • some do matriphagy - which is when the embryos eat the mother's skin that she regrown

Amphibian definition

means both ways of life

• which refers to the metamorphosis of an aquatic larva into a terrestrial adult

  • they have moist skin and complements the lungs in gas exchange

  • fertilization is external in most species & the eggs require moist environment

Amniotes definition

a groud of tetrapods whose living members are reptiles, birds and mammals

Amniote derived characteristic

the derived characteristic of amniotes is the amniotic egg

• it contains membranes that protect the embryo

  • the extraembryonic membranes are:

    • amnion

    • chorion

    • yolk sac

    • allantois

Amnion membrane

The amnion protects the embry in a fluid filled cavity that cushions against mechanical shock

Allantois membrane

the allantois is a disposal sac for certain metabolic wastes produced by the embryo

Chorion membrane

The chorion membrane exchanges gases with the allantois membrane between the embryo and the air

Yolk sac

The yolk sac contains the yolk, a stockpile of nutrients. other nutrients are stored in the albumen, also known a egg white.

Amniote terrestrial adaptations

the terrestrial adaptation amniotes are:

• relatively impermeable skin

• the ability to use the rib cage to ventilate the lungs

what was the origin and radiation of amniotes

the most recent ancestor of living amphibians and amniotes lived about 350 mya

• early amniotes resembled small lizards with sharp teeth, which is a sign they were predators

Clade Reptiles

this clade includes the tuataras, lizards, snakes, turtles, crocodilians, birds, and the extinct dinosaurs.

• key features are scales which create a waterproof barrier

  • they lay shelled eggs on land

The origin and evolutionary radiation of reptiles

The oldest reptilian fossils date from the late Carboniferous, 310mya

Ectothermic vs Endothermic

Reptiles are ectothermic

• which means they have to absorb external heat as the main source of body heat

  • e.g. sunbathing

Birds are endothermic

• this means they are capable of keepthing the body warm through metabolism

What is the two surviving lineage of lepidosaurs

The two surviving lineages of the lepidosaurs is the:

• tuatara

  • this is a species of lizard-like reptile

    • these have a third (parietal) eye

• squamates

  • includes lizards and snakes

    • they are the mose numerous and diverse reptiles

      • snakes are legless liposaurs that evolved from lizards

Turtles and tortoises

Turtles are the most distinctive group of reptiles alive today

• all tutles have a boxlike shell amde of upper & lower shields that are fused to the vertebrae, clavicles and ribs

  • some turtles have adapted to deserts and others live entirely in ponds and rivers

Alligators and crocodiles

Crocodilians (alligators and crocodiles) belong to an archosaur lineage that dates back to the late Triassic

• has more than 2 dozen species

Birds

Birds are archosaurs

• however every feature of their reptilian anatomy has undergone modification in their adaptation to flight

  • has about 10000 species

Derived characters of Birds

Many of their characters are adaptations to facilitate flight

• the major adaptation in the wings is the keratin feather

  • others include lack of a urinary bladder, females have one ovary, small gonads and loss of teeth

What does a feather consist of?

A feather consists of a central air-filled shaft from which radiate the vanes

• the vanes are made up of barbs with small branches called barbules

How does flight help birds?

Flight enchances hunting, scavenging, escape from terrestrial predators and migration

• flight requires a great expenditure of energy, acute vision and fine muscle control

The origin of birds

Birds probably descended from small therapods, which is a group of carnivorous dinosaurs

• by 150mya feathered therapods had evolved into bired

  • Archaeopteryx remains the oldest bird known (150 mya) though another recently described fossil named Xiaotingia is to be a bird-liked featehred dinosaur (155 mya)

What are mammals?

They are amniotes that have hair a produce milk via mammary glands

Derived characteristics of mammals

1. Mammary glands that produce milk

2. Differentiated teeth

3. Efficient repsiratory and circulatory systems

4. Relatively large brain

5. Hair

Early evolution of mammals

Mammals and reptiles are sister groups

• meaning they came from a common ancestor

  • they have been separated for more than 300 mil. years

    • Mammals evolved from synapsids in the later Triassic period

  • Non-mammalian synapsids lacked hair and laid eggs

What were the 3 living lineages of mammals that emerged in the EARLY CRETACEOUS

1. Monotremes

2. Marsupials

3. Eutherians

monotremes

Includes the platypus and 4 species of spiny anteaters, totalling 5 species of monotremes

• they are only found in Austrailia and New Guinea

  • Monotremes have hair and produce milk through their skins

    • meaning they lack nipples

      • They are the only mammals that lay eggs (inset)

Marsupials

Includes kangaroos, opossums and koalas

• Marsupials have 324 species

  • they have nipples that provide milk and give birth to live young

    • however offspring the offspring are born early in their development

      • the emebryo develops in a placenta in the uterus

      • then they finish their growth while nursing from a nipple in their mother's pouch called a marsupium

Eutherians

Includes primates, whales, rodents and many others

• has the most mammals with 5010 species

  • EUtherians have a longer pregnancy than marsupials and have a more complex placenta

    • a placenta is a structure which nutrients diffuse into the embryo from the mother's blood

      • Young eutherians complete their embryonic development in the uterus joined to the mother by the placenta

Order Primates

Includes lemurs, tarsires, monkeys and apes

• humans are members of the ape group

  • earliest primates were tree dwellers

Derived characters of Primates

1. Most primates have hands and feet adapted for grasping

• Monkeys and apes have an opposable thumb

2. A large brain and short jaws

3. Forward-looking eyes close together on the face which provides depth perception

4. Complex social behaviour & parental care

Early human ancestors

Humans diverged from other apes about 6-7 million years ago in Miocene

• Hominins are more closely related to humans than to chimpanzees

• The old hominin fossils are Sahelanthropus tchadensis which lived 6.5 mya

Hominin evolution

Early hominins had a small brain but probably walked upright

• Ardiphithecus ramidus (4.4 mya) was bipedal but had a brain of only 325 cm³ in volume, much smaller than Homo sapiens (1300 cm³)

Australopiths

These are a paraphyletic assemblage of hominins living between 4 and 2 mya

• some species walked fully erect

Early Homo

The earliest fossils placed in our genus Homo are those of Homo habilis ranging in age from 2.4-1.6 mil. years

• brain 675 cm³

• Stone tools have been found with this species which lead to it's name “handy man”

Homo erectus

Homo erectus left Africa by 1.8 mya

• it was the first hominin to leave Africa

  • it became extinct 50000 to 200000 years ago

Homo Bodoensis

In 2021 a team lead by a UofW paleoanthropologist, Mirjana Roksandic added Homo bodensis to the Hominin family tree

• Homo bodoensis lived in Africa and south eastern Europe 770000 to 126000 years ago

  • They suggest it was the direct ancestor of Homo sapiens

Neanderthals

also known as Homo neanderthalensis lived in Europe and the Near East from 200000 to 28000 years ago

• They were thick- boned with a larger brain than Homo sapiens

  • They buried their dead, made hunting tools and interbred with Homo sapiens

Homo sapiens

Our species appeared in Africa by 195000 years ago, maybe even earlier

• All living humans are descended from these african ancestors

• Oldest fossils outside Africa are from Middle East and date back 115000 years ago

  • The spread beyond Africa in one or more waves

    • They reached Austrailia 50000-70000 years ago

    • Humans first arrived in the New World sometime before 15000 years ago

Ecological effects of animals: Marine Ecosystems

In marine ecosystems have an abundance of cyanobacteria decreased in the early Cambrian

• this decrease may have been caused by the activities of crustaceans and other animals with suspension feeding mouthparts

  • causes algae to require more light for photosynthesis than do cyanobacteria

    • this caused an increase in cyanobacteria abundance and moved to deeper water

Ecological effects of animals: Terrestrial ecosystems

Before animals joined plants and fungi onshore, terrestrial ecosystems had a simple structure

• Producers (early plants) harnessed energy from the sun and drew nutrients from the soil

  • while decomposers (fungi & bacteria) returned nutrients to the soil

• by 410 mya animals had transformed these ecosytems

  • Plants were eaten by herbivores

    • Herbivores were then eaten predators

      • Detritivores consumed organic debris

An example of ecological effects of animals

Lesser snow geese breed in marshlands alongside Hudson Bay

• The geese feed on grasses and other marsh plants

  • At low population numbers, lesser snow geese improve the growth of marsh plants because the defecate every few minutes

  • At high numbers the geese can destroy the marsh which causes a wipe out in the vegetation

So what did the rise of animals cause?

The rise of animals set in motion a series of profound evolutionary changes such as,

• The origin of mobile, heterotrophic animals with a complete digestive tract drove some species to extinction

• and initiated ongoing arms races between bilaterian predators and prey

  • This drive sinteractions between species

What does interactions species cause?

Two species that interact can exert selective pressures on each other

• this is called reciprocal selection

  • essentially a characteristic of a certain species can influence the evolution of another species that interacts with it

    • e.g. Madagascar orchid secretes nector near the base of a long floral tube which influenced the development of a long tongue in a moth

Human impacts on evolution

Humans make changes to the environment which can alter the selective pressures faced by many species

• which should not be surprising by evolutionary responses

  • e.g. harvested populations

Human impacts on evolution: Harvesting populations

Harvesting older and larger fish has been shown to reduce the age and size at maturity in a number of species including the Atlantic cod

• This is due to the way fisheries fish them with nets

  • this caused the Atlantic cod to have a decrease in larger fish which meant evolution began selecting for smaller fish to avoid being caught in the net

    • the age at sexual maturity has declined over time which meant they mature at a smaller size