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Biology > Animal Diversity I > Flashcards

Animal Diversity I Flashcards

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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
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2
Q

How do animals reproduce?

A

Most reproduce sexually, with a dominant diploid stage

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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)
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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
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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
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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?
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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
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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
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9
Q

When was the Mesozoic ear?

A

(251-65.5 MYA)

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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
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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
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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

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13
Q

What is the Phylogenetic tree of animals based on?

A

Similarities in:
» DNA sequence
» Morphology
» “Body plan”

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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
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15
Q

What are the main features of body plans as they developed throughout evolution of animals?

A
  1. Development of true tissues
  2. Development of bilateral symmetry
  3. Protostome vs deuterostome
    development
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16
Q

How many distinct points of division are there in current animal phylogeny?

A

4

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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

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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)
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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
Q

What are the three stages of early development of the embryo?

A

1) Cleavage
2) Coelom formaion
3) Fate of the blastopore

26
Q

What is the 4th step of the division of animal phylogeny

A

= Ecdysozoa = moult;

- Lophotrochozoa = either lophophore or trochophore

27
Q

What are parametazoa?

A

animal with no ecto or endoderm

28
Q

What are Eumetazoa?

A

Animals whose tissue are organized into true tissues and there is a development of organs

29
Q

What are Porifera?

A

(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
Q

What is the anatomy of porifera

A
  • Lack true tissues, but have ≠ types of cells
31
Q

What are Cnidaria

A 
(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
Q

What is the anatomy of a Cnidaria?

A
  • Sac with central digestive compartment (“gastrovascular cavity”)
  • Single opening, both mouth and anus
  • 2 variations
    » Mostly sessile polyp and mobile medusa
33
Q

What are Cnidocytes?

A

Cnidarians are predators
» Use tentacles to capture prey
» Cnidocytes are specialised cells that throw nematocysts (similar to harpoons)

34
Q

What is coral made of?

A
  • Coral polyps secrete a hard exoskeleton of calcium carbonate
    » Skeleton is what we think of as “coral”
  • Corals form symbiosis with algae
35
Q

What are protostomes

A
  • 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
Q

What are Arthropods?

A
  • 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
Q

what is the general anatomy of an arthropod?

A

Success has been attributed to body plan
» Segmented body (developmental flexibility)
» Jointed appendages
» Hard exoskeleton

38
Q

What is an arthropods exoskeleton made of?

A

Exoskeleton made of protein and polysaccharide (chitin)

39
Q

What are some of the advantages of having an exoskeleton?

A

Many advantages:
» Avoid water loss → facilitate colonisation of land
» Defense against predators
» Provides point of attachment for muscles

40
Q

What is the major draw back of having an exoskeleton?

A

Molting (“ecdysis”, hence the group’s name)
» Must be shed for animal to grow
» Molting is energetically expensive
» Newly molted animals temporarily vulnerable

41
Q

What areas are insect common in and why are they important?

A
  • Common in terrestrial, freshwater and air
    » Rarer in marine habitats
  • Play an enormous biological role
    » Herbivore, predator, parasite, prey, pollinator
42
Q

When was the explosion of diversity in insects and what was in due to?

A

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
Q

What are Lophotrochozoa?

A
  • 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
Q

What are some examples of Lophotrochozoa?

A 
- 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
Q

What are mollusca?

A
  • 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
Q

What is the anatomy of a mollusc?

A

All have a similar body plan
» Muscular foot → movement
» Visceral mass with most organs
» Mantle → drapes over visceral mass, secretes shell

47
Q

What are some examples of mollusca?

A
  • 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

Biology (27 decks)

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