Animal Diversity I Flashcards
1
Q
What distinguishes animals?
A
- A combination of defining features:
» Eukaryotic
» Multicellular
» Heterotrophs
≠ plants, which are autotrophs
≈ fungi, except that fungi digest food outside and then absorb, while animal ingest and then digest
» No cell wall (≠ plants and fungi), but specialised support structure (collagen) and unique intercellular junctions
» Have nervous tissue and muscle tissue → move
2
Q
How do animals reproduce?
A
Most reproduce sexually, with a dominant diploid stage
3
Q
What are Hox genes and what are they used for?
A
- Most (not all) animal life cycles include a larval stage that metamorphoses into adult
- Hox genes: developmental genes that regulate expression of other genes, particularly during embryonic development (ie, control body plan)
4
Q
When did animals first appear?
A
- Molecular clocks and
biochemical fossil record suggest that common ancestor to all animal species lived about 770 million YA - Animals (sponges) appear ≈700 million YA
5
Q
What lived in the first 150 million years of the early earth?
A
- Oldest fossilised animals discovered in Ediacara Hills, SA (similar fossils since found elsewhere)
- Mainly soft-bodied animals:
» Molluscs
» Sponges
» Cnidarians (sea anemone) - Early evidence of predation
6
Q
What happened in the Cambrian Explosion 530 MYA?
A
- Huge increase in diversity in early Cambrian
» Can suddenly find fossils of about 50% of all extant (living) animal phyla, esp. bilaterians - Simultaneous decrease in Ediacarian life forms
• Predation?
7
Q
What caused the Cambrian Explosion?
A
- Predator – prey “arms race”?
- Response to increased in atmospheric O2?
- Development of Hox genes and microRNAs?
» The IKEA of developmental biology
8
Q
What happened during the Paleozoic period?
A
- Animal diversity continued to increase
» Punctuated by mass extinction events - Vertebrates (fish) emerged as top predators in marine food web
- Colonisation of land
» Fungi, plants ≈ 500 MYA
» Arthropods ≈ 450 MYA
» Vertebrates ≈ 365 MYA → amphibians, amniotes
9
Q
When was the Mesozoic ear?
A
(251-65.5 MYA)
10
Q
What happened during the Mesozoic era?
A
- Starts with mass extinction event (84% genera disappear)
- Surviving animals spread into new habitats
» Coral reefs appear - Descent with modification in vertebrates:
» Origin of wings in birds
» Emergence of small and large dinosaurs
» Appearance of the first small mammals
11
Q
What happened dureing the Cenozoic era and when was it?
A
- (65.5 MYA to present)
- Starts with mass extinction event (47% †)
» Disappearance of large, nonflying dinosaurs and marine reptiles
» Rise of large mammals, as they exploit the vacated ecological niches
12
Q
how many phyla are there currently
A
there are 35 and all but 1 are invertebrates
- Chordate Phylum = vertebrates
About half are exclusively marine
13
Q
What is the Phylogenetic tree of animals based on?
A
Similarities in:
» DNA sequence
» Morphology
» “Body plan”
14
Q
What does body plan mean?
A
- particular set of morphological and developmental traits of living organisms
- Body plans reflect evolution → can help build animal phylogenetic tree
15
Q
What are the main features of body plans as they developed throughout evolution of animals?
A
- Development of true tissues
- Development of bilateral symmetry
- Protostome vs deuterostome
development
16
Q
How many distinct points of division are there in current animal phylogeny?
A
4
17
Q
What is the first step of the division of animal phylogeny
A
Step 1: Development of true tissues
- Tissue = collection of cells that act as a functional unit and deliver a specialised function
18
Q
What happens in the first step of the division of animal phylogeny?
A
- In most animals, embryo becomes layered during early development
- Earlier animals have 2 layers (“diploblastic”)
» Outside layer (ectoderm) → outer covering (and central nervous system)
» Inner layer (endoderm) → digestive tract and organs - Later animals have a 3rd layer (“triploblastic”)
» Middle layer (mesoderm) → muscles and other organs (and body cavity)
19
Q
What is the 2nd step of the division of animal phylogeny
A
Step 2: Development of bilateral symmetry
20
Q
What happens in the 2nd step of the division of animal phylogeny
A
- Early life forms with tissues have radial symmetry
» 1 axis of orientation: top and bottom - Later organisms developed bilateral symmetry
» Multiple axes of orientation: dorsal vs ventral, left vs right, anterior (sensory organs) vs posterior
21
Q
What is the 3rd step of the division of animal phylogeny
A
Step 3: Differences in embryonic development
22
Q
How many embryonic layers do Radially symmetrical & Bilaterally symmetrical animals have?
A
- In most animals, embryo becomes layered during early development
- Radially symmetrical animals have 2 layers (“diploblastic”)
» Outside layer (ectoderm) → outer covering (and central nervous system)
» Inner layer (endoderm) → digestive tract and organs - Bilaterally symmetrical animals have a 3rd layer (“triploblastic”)
» Middle layer (mesoderm) → muscles and other organs (and body cavity)
23
Q
What happens in the 3rd step of the division of animal phylogeny
A
- Most triploblastic animals have a body cavity (“coelom”)
» Fluid- or air-filled space between digestive tract and outer body wall - Has many functions:
» Acts to cushion suspended organs
» Allows internal organs to move independently of outer body wall
» In soft-bodied organisms (eg earthworms), non-compressible fluid can act like a skeleton against which muscles can work
24
Q
What is the differentiation between animal body plan based on?
A
Early development of the embryo
25
What are the three stages of early development of the embryo?
1) Cleavage
2) Coelom formaion
3) Fate of the blastopore
26
What is the 4th step of the division of animal phylogeny
= Ecdysozoa = moult;
| - Lophotrochozoa = either lophophore or trochophore
27
What are parametazoa?
animal with no ecto or endoderm
28
What are Eumetazoa?
Animals whose tissue are organized into true tissues and there is a development of organs
29
What are Porifera?
(Parametazoa)-“Sponges”
» Porifera = “pore bearers”
» Sessile (ie, don’t move)
» Often brightly coloured
» Initially mistaken for plants by ancient Greeks
» Size from mm → m
» Filter feeders – trap food particles in water as they draw it through their body
30
What is the anatomy of porifera
- Lack true tissues, but have ≠ types of cells
31
What are Cnidaria
```
(Eumetazoa)
- Diverse range of sessile (radical symmetry) and motile forms
» Hydra
» Sea anemone
» Coral
» Jellyfish
- Simple diploblastic radial body plan
- No centralised brain, but have nerves associated with sensing
```
32
What is the anatomy of a Cnidaria?
- Sac with central digestive compartment (“gastrovascular cavity”)
- Single opening, both mouth and anus
- 2 variations
» Mostly sessile polyp and mobile medusa
33
What are Cnidocytes?
Cnidarians are predators
» Use tentacles to capture prey
» Cnidocytes are specialised cells that throw nematocysts (similar to harpoons)
34
What is coral made of?
- Coral polyps secrete a hard exoskeleton of calcium carbonate
» Skeleton is what we think of as “coral”
- Corals form symbiosis with algae
35
What are protostomes
- Part of the Ecdysozoa group (Eumetazoa)
- Very diverse animal clade
» Includes 8 phyla
» Contains more known species than all other animal, protists, fungi and plant groups combined!
- Includes animals that shed tough external coat as they grow (ecdysis = moulting)
- Two largest phyla:
» Nematodes (roundworms)
» Arthropods
36
What are Arthropods?
- A Phyla of the Protostomes group (Eumetazoa)
- One of the most successful animal phyla
» More than 1,000,000 species of arthropods described (most are insects)
» Found in nearly all habitats of biosphere
» Estimated 1018 arthropods living on Earth
- Includes:
» Chelicerates (scorpions)
» Myriapods (millipedes)
» Crustaceans
» Insects
37
what is the general anatomy of an arthropod?
Success has been attributed to body plan
» Segmented body (developmental flexibility)
» Jointed appendages
» Hard exoskeleton
38
What is an arthropods exoskeleton made of?
Exoskeleton made of protein and polysaccharide (chitin)
39
What are some of the advantages of having an exoskeleton?
Many advantages:
» Avoid water loss → facilitate colonisation of land
» Defense against predators
» Provides point of attachment for muscles
40
What is the major draw back of having an exoskeleton?
Molting (“ecdysis”, hence the group’s name)
» Must be shed for animal to grow
» Molting is energetically expensive
» Newly molted animals temporarily vulnerable
41
What areas are insect common in and why are they important?
- Common in terrestrial, freshwater and air
» Rarer in marine habitats
- Play an enormous biological role
» Herbivore, predator, parasite, prey, pollinator
42
When was the explosion of diversity in insects and what was in due to?
Explosion of species diversity 359-251 MYA, likely due to a combination of:
» Response and co evolution with new plant species (gymnosperms and angiosperms) → diversity of insects linked to diversity of angiosperms
» Evolution of flight
43
What are Lophotrochozoa?
- Protostomes (Eumetazoa)
- Name refers to 2 features observed in some animals in this clade:
» Lophophore: crown of tentacles for feeding [lophos = crest; pherein = to carry]
» Trochophore larvae: free-swimming planktonic larval stage
44
What are some examples of Lophotrochozoa?
```
- Platyhelminths (flatworms)
» Free-living: planarians
» Parasitic: tapeworm
- Syndermata
» Recently established, includes rotifers (microscopic multicellular animals w/ complex organs) and parasitic taxa
- Ectoprocts
» Colonies look like clump of moss
- Lamp shells
» Look like clams
- Molluscs → very diverse phylum!
- Segmented worms
» Mobile or sedentary
» <1 mm → >3 m
```
45
What are mollusca?
- Very diverse phylum
100,000 species)
- Soft-bodied, most secrete hard protective shell made of calcium carbonate
» Slugs, squids and octopuses have (reduced) internal shell or have lost it altogether
- Most molluscs have separate sexes (Except snails)
- Life cycle of many
marine molluscs include a trochophore larval stage
46
What is the anatomy of a mollusc?
All have a similar body plan
» Muscular foot → movement
» Visceral mass with most organs
» Mantle → drapes over visceral mass, secretes shell
47
What are some examples of mollusca?
- Gastropods (75%): Snails and slugs
» Most have a (single) shell, found in marine, freshwater and on land
- Bivalves: Oysters and clams
» Shell in two halves, sedentary suspension feeders
- Cephalopods: Octopuses and squids
» Internal “shell”, modified foot → siphon, predators
