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Chapter 15 Animal Evolution: the
evolution of vertebrate
主講人: 張慧雲 老師
(Hui-Yun Chang, Ph.D.)
清華醫學科學系
Institute of Systems Neuroscience
Tel: 03-574-2778
Email: [email protected]
[email protected]
Human and Animals
Humen and Animals
Human and Animals
Human and Animals
15.4 What is the Chordates (Chordata)

Four embryonic features help define chordates:
1. A dorsal supporting rod: notochord
2. A dorsal hollow nerve cord (which becomes a
brain and spinal cord)
3. A pharynx with gill slits: a feeding device
4. A tail extending past the anus
Chordates (Chordata)
 Chordates
• Includes invertebrate and
vertebrate groups
 Notochord
• Stiff rod of connective
tissue that runs the
length of the body in
chordate larvae or
embryos
The Invertebrate Chordates
 There are two groups of invertebrate
chordates – both are marine organisms
 Tunicates
• Invertebrate chordates that lose their defining
chordate traits during the transition to adulthood
 Lancelets
• Invertebrate chordates that have a fishlike shape
and retain defining chordate traits into adulthood
Tunicates: 2,500 species
Lancelets: 25 species
Fig. 15-18 (photo), p. 305
Animation: Tunicate body plan
Animation: Lancelet body plan
Vertebrate Traits and Trends

Most chordates are vertebrates (having a
backbone)

Five key innovations made adaptive radiation
of vertebrates possible
5 Key Innovations in Vertebrates

Vertebral column (backbone)

Jaws
•

Hinged skeletal elements used in feeding
Amniote eggs
•
Waterproof egg found in land tetrapods (reptiles,
birds, and mammals)
5 Key Innovations in Vertebrates

Gas exchange organs
•
•

Swim bladder (organ that adjusts buoyancy in
bony fishes)
Lungs (saclike organs inside which blood
exchanges gases with the air)
Four bony limbs
•
Tetrapod (vertebrate with four limbs)
Chordate Family Tree
Fig. 15-20a, p. 307
Animation: Jawless fishes
Lancelets Tunicates
Jawless Cartilaginous
Fishes
Fishes
Bony
Fishes
Amphibians
Reptiles,
Birds
Mammals
5 Amniote eggs
4
3
2
1
Four limbs
Swim bladder or lungs
Jaws
Backbone
invertebrate
ancestor
Fig. 15-19, p. 306
Animation: Vertebrate evolution
15.5 Fins to Limbs –
Fishes and Amphibians
 All vertebrates have a brain, a closed circulatory
system with one heart, a complete digestive
system, and a urinary system with two kidneys
 Kidney
• Organ of the vertebrate urinary system that filters
blood and adjusts its composition
Fishes
 Fish were the first vertebrate lineage to evolve
• Like most vertebrates, fish have a cloaca
 Fish
• Aquatic vertebrates
• The oldest and most diverse vertebrate group
 Cloaca
• A body opening that functions in reproduction and
elimination of urinary and digestive wastes
The Jawless Lampreys
 Lampreys are an evolutionarily ancient lineage
of fishes with no jaws or fins
• Backbone of cartilage
 Some lampreys are parasites of other fishes
Fish Diversity
Jawed Fishes
 Most jawed fishes have paired fins and scales
 Scales
• Hard, flattened elements that cover the skin of
some vertebrates
 There are two groups of jawed fishes
• Cartilaginous fishes
• Bony fishes
Animation: Evolution of jaws
Cartilaginous Fishes
 Cartilaginous fish
• Fish with a skeleton of cartilage
• Example: sharks
 Not all sharks have sharp teeth, some are filter
feeders or bottom feeders
Animation: Cartilaginous fishes
Bony Fishes
 Bony fishes are the most diverse vertebrates
 Bony fishes
• Jawed fishes in which the embryonic skeleton of
cartilage is mostly transformed to bone in adults
• Have protective gill covers and swim bladders
Two Subgroups of Bony Fishes
 Ray-finned fish
• Include food fishes such as salmon and tuna
• Fins are supported by thin rays derived from skin
 Lobe-finned fish
• Include coelacanths and lungfishes
• Have fins with bony supports
• Have gills and lunglike sacs
Bony Fish Innovations
Fig. 15-20b, p. 307
dorsal fin
pectoral fins
Fig. 15-20b, p. 307
Fig. 15-20c, p. 307
swim bladder
kidney
ovary
nerve cord
brain
cloaca
intestine
stomach liver
heart
gills
Fig. 15-20c, p. 307
Animation: Bony fish body plan
Early Tetrapods
 All land vertebrates are descendents of an
ancient lobefinned fish
 Adaptations allowed swimmers to become fourlegged walkers (tetrapods)
• Pelvic and pectoral fins became limb bones
• Three-chambered heart provides blood flow to
lungs
Transition to Tetrapods
Animation: Evolution of limb bones
Modern Amphibians
 Amphibians, the first tetrapods on land, spend
time on land but require water to breed
• Include salamanders, frogs, toads
• Many species are now threatened or endangered
 Amphibian
• Tetrapod with a three-chambered heart and
scale-less skin; aquatic larvae have gills, adults
live on land as carnivores with lungs
Amphibians
Amphibians
Animation: Salamander locomotion
15.6 Adapt to dry land, and away from Water –
The Amniotes
 Amniotes were the first vertebrates that did not
require external water for reproduction
 The First: an egg with a shell, amniote eggs
 The Second traits: Their skin and kidneys
conserve water.
Amniotes
 Amniote
• Vertebrate that produces amniote eggs
• A reptile, bird, or mammal
 Amniote egg
• Egg with four membranes that allows an embryo
to develop away from water
Amniote Egg
yolk sac
embryo
hardened shell
amnion
chorion
allantois
albumin (“egg white”)
Fig. 15-24a, p. 310
Animation: Amniote egg
Modern Amniotes
mammals
turtles
lizards, snakes
crocodilians
birds
Fig. 15-24b, p. 310
Amniote Innovations
 Some early amniotes evolved an ability to
regulate internal body temperature
 Ectotherm (“cold-blooded”)
• Animal that gains heat from the environment
• Fish, amphibians, turtles, lizards, snakes
 Endotherm (“warm-blooded”)
• Animal that produces its own heat
• Birds and mammals
Reptile Diversity
 An early branching of the amniote lineage
separated ancestors of mammals from the
common ancestor of reptiles
 Reptile
• Amniote group that includes lizards, snakes,
turtles, crocodilians, birds, and extinct dinosaurs
Lizards and Snakes
 Lizards are the most diverse reptile subgroup
• Typically predators that lay eggs outside the body
 Snakes evolved from ancestral lizards
• Carnivores with flexible jaws for swallowing prey
• Most hold eggs in the body and give birth to live
young
Turtles and Crocodilians
 Turtles and tortoises are covered with a bony
shell that connects to the backbone
• Turtles spend most of their life in or near water
• Tortoises are land-dwelling plant eaters
 Crocodilians, the closest living relatives of birds
• Predators that lay eggs and care for the young
Reptiles
Animation: Tortoise shell and skeleton
Animation: Crocodile body plan
Birds
 Bird
• The only modern amniote with feathers (modified
scales adapted for flight); parenting (adults of all
bird species attend their offspring, warn and
protect them from predators)
 Adaptations for flight: the cerebellum enlarged
• Feathers and wings
• Lightweight bones
• Efficient respiratory system and four-chambered
heart
An Owl in Flight
An Diversity of Birds: 8,600 species
Animation: Avian bone and muscle
structure
Animation: Feather development
Mammals: simplified skeletons, 4000 species
 Mammals
• The only amniotes that nourish their young with milk from
mammary glands
• Eggs are fertilized within the female’s body.
• Hair except whales and dolphins
• Teeth
• Weight: 2g-blue whale (31meters 160,000kg)
 There are three lineages of mammals:
• Monotremes (egglaying mammals)
• Marsupials (pouched mammals)
• Placental mammals (a placenta provides nutrients to
developing offspring)
Three Lineages of Mammals
Mammals: simplified skeletons, 4000 species
 There are three lineages
of mammals:
• Monotremes (egglaying
mammals)
• Marsupials (pouched
mammals):240 species
• Eutherians (Placental)
mammals (a placenta
provides nutrients to
developing offspring)
Three Lineages of Mammals
 Only three species of monotremes survive, and
most marsupials live in Australia or New Zealand
 Eutherians(Placental) mammals are the most
diverse group and have displaced others in most
habitats, Higher metabolic rate, better
temperature controls, more efficient nourishment
of embryos: almost 4000 species
Mammals: The diversity of Eutherians
 The Rodents: 1,700
species
The bats: 850
species
and many others
 Marine mammals:
whales
dolphins
seals
sea lions
Animation: Mammalian radiations
Animation: Mammalian dentition
Animation: Structure of the placenta
Video: ABC News: Dinosaur discovery
Video: ABC News: Chickens have a new
ancestor
The major traits of primates
 Five trends define the lineage leading to primates
• Hands adapted to grasp branches and nails rather
than claws
• Eyes on the front of the face: good depth
perception
• Upright standing and walking (bipedalism)
• very small offspring and receive extended parental
care
• Evolution of brain, behavior, and culture
15.7 From Early Primates to Humans
 The hominoid branch of the primate family tree
evolved in Africa; it includes apes and hominids
 Primate
• Have five-fingered hands capable of grasping
• Includes tarsiers, moneys, apes, and humans
 Hominid
• Humans and extinct humanlike species
Primate Classification
Prosimians: tarsiers
Anthropoinds: descended to the ground
Some Primates
Primate Classification
Hominoids to Hominids
 Hominoids appeared about 23 mya, but most
died out; hominids appeared 6 to 8 mya
 Hominoids
• Apelike species
 Australopiths
• Early hominids that walked upright
• Collection of now-extinct lineages, some of which
may be ancestral to humans
Footprints Left by Bipedal Hominids
Emergence of Early Humans
 Humans are characterized by analytical and
verbal skills, complex social behavior, and
technological innovation
 Humans
• Members of the genus Homo
Emergence of Early Humans
 The first known members of genus Homo (H.
habilis) lived in Africa between 2.4 and 1.6 mya
 Human traits associated with H. habilis
•
•
•
•
Bipedalism
Manual dexterity and use of stone tools
Larger brain volume
Small face and thickly enameled teeth
Homo habilis
Emergence of Early Humans
 H. erectus was the first hominid to migrate out of
Africa, 1.7 million years ago
 H. erectus developed into new species
• H. neanderthalensis (Neandertals)
• H. floresiensis
• H. sapiens (modern humans) 190,000 years ago
Origin and Extinction
of Three Hominid Genera
Homo rudolfensis
Australopithecus
anamensis
Homo floresiensis
Homo
sapiens
Homo habilis
Australopithecus africanus
Homo erectus
Australopithecus garhi
Australopithecus afarensis
Paranthropus
aethiopicus
Homo
neanderthalensis
Paranthropus robustus
Paranthropus boisei
4
3
2
1
present
Time (millions of years ago)
Fig. 15-30, p. 315
Australopithecus to Homo erectus
Australopithecus
africanus
Paranthropus boisei
Homo habilis
Homo erectus
Fig. 15-29 (a-d), p. 314
Recent Homo Species
Homo sapeiens
 Larger brains
• An increasing complex social life
 Language and culture
Where Did Modern Humans Originate?
 Multiregional model
• H. sapiens populations in different regions
evolved from H. erectus in those regions
 Replacement model
• H. sapiens evolved in Africa, then migrated to
different regions and replaced the other hominids
that lived there
Two Models for the Origin of H. sapiens
H. erectus
H. sapiens
Africa
Asia
A
Europe
H. erectus
H. sapiens
Africa
Asia
B
Europe
Time
Fig. 15-33, p. 316
Animation: Primate evolutionary tree
Animation: Genetic distance between
human groups
Video: ABC News: Ancient human skull
Animation: Primate skeletons
Animation: Skulls of extinct primates
Animation: Fossils of australopiths
Animation: Homo skulls
15.8 Impacts/Issues Revisited
 Scientists disagree over interpretations of new
fossils such as Homo floresiensis – is it really a
new species?
 Further study of existing fossils, searching for
new fossils, or DNA studies may help test
competing hypotheses