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General Biology: OrganismL Biology and Evolution - Set 1 > Introduction to Animals > Flashcards

Introduction to Animals Flashcards

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1
Q

Nutritional Mode

A

Animals are heterotrophs that ingest their food
- Need to consume organic substrates in order to grow
- Typically have some sort of orifice through which food enters

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2
Q

Cell Structure

A
  • Animals are multicellular eukaryotes
  • Animal cells lack cell walls
  • Tissues are held together by structural proteins such as collagen
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3
Q

What kind of cells are unique to animals?

A

Specialized neural cells and muscle cells
- Nervous system allows perception of noxious or favorable environmental conditions, predators, prey
- Muscle tissue allows the animal to respond to environment or stimuli

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4
Q

Cleavage

A

Mitotic cell divisions which lead to the formation of the blastula
- In most species, a small flagellated haploid sperm fertilizes a larger, haploid, non-motile, polarized egg
- In protostome development, cleavage is spiral and determinate
- In deuterostome development, cleavage is radial and indeterminate
- With indeterminate cleavage, each cell in the early stages of cleavage retains the capacity to develop into a complete embryo

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5
Q

Larva

A

The sexually immature & morphologically and ecologically distinct from the adult
- They eventually undergo metamorphosis, transforming into an adult

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6
Q

What kind of genes are unique to animals?

A

Most animals have homeobox-containing family of genes called Homeotic or Hox genes
- Transcription factors that regulate the genes that control development of body form
- May have arisen in the eukaryotic lineage that gave rise to animals

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7
Q

Who won the nobel prize for medicine in 1995 and why?

A

Edward B. Lewis, Christiane Nusslein-Volhard and Eric Wieschaus for discoveries concerning “ the genetic control of early embryonic development

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8
Q

What did Lewis find from his experiment on flies?

A

He found a cluster of homeotic (Hox) genes in the chromosome and colinearity in time and space
- The gene order in the cluster mimics the order of expression of genes and their function along the anterior-posterior (A-P) body axis
- Exhibit temporal colinearity - anterior genes expressed first during development and posterior later

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9
Q

Duplication of Hox genes

A
  • First duplication ~520 MYA
  • Duplication of cluster provided ‘extra’ regulatory control to direct new body plans, eg. vertebrae
  • Second duplication ~425 MYA
  • Further duplication of cluster provided even greater regulatory control allowing greater structural complexity
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10
Q

What was most likely the first common ancestor of living animals?

A

Probably a colonial flagellated protist related to choanoflagellates, a group that arose about a billion years ago, may have lived between 675 and 875 mya

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11
Q

What is the main evidence that choanoflagellates are related to animals?

A
  • Sequence data indicates that Choanoflagellates and animals are sister groups
  • Collar cells only found in animals and not in protists
  • Choanoflagellate cells resemble sponge collar cells
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12
Q

What do colonies rapidly invert their curvature in response to?

A

Changing light levels
- Inversion may be a primitive form of contraction
- These findings may inform reconstructions of hypothesized animal ancestors that existed before the evolution of specialized sensory and contractile cells

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13
Q

Snowball Earth

A
  • Geologic evidence for a “snowball Earth” from 750 to 570 MYA
  • May have limited diversity & distribution of higher eukaryotes until very late Precambrian
  • Diversification of higher eukaryotes appears with thawing snowball Earth thawed 565 MYA`
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14
Q

Neoproterozoic Era

A

1 Billion - 542 MYA
- Recent chemical evidence (steroids) of presence of sponges i S. Oman >635 mya (represents oldest evidence for animals in the fossil record)
- Early members of the animal fossil record include the Ediacaran biota, which dates from 565 to 550 mya

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15
Q

Precambrian fossil animals of the Ediacara Hills

A

In 1946, mining geologist R.C. Sprigg discovers these fossils - dated as 560 MY old

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16
Q

Early embryos found in China

A

Recent fossils finds from the Doushantou Formation in China have produced a diversity of algae and animals from 570 mya, including supposedly beautifully preserved embryos

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17
Q

Paleozoic Era

A

542-251 million years ago
- Vertebrates made the transition to land around 360 mya
- Animals began to make an impact on land by 460 mya
- The Cambrian explosion (535 to 525 million years ago) marks the earliest fossil appearance of many major groups of living animals

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18
Q

The Burgess Shale

A

THe Burgess Shale in the Canadian Rockies holds the remains of an ancient sea from 530 mya
- Was discovered by Charles Walcott in 1909

19
Q

Causes of Animal Diversification

A
  • Ecological Causes: Emergence of predator-prey relationships led to diversity of evolutionary adaptations, such as variations kinds of protective shells and diverse modes of locomotion
  • Geological Causes: Atmospheric oxygen may have finally reached high enough concentrations to support more active metabolism
  • Genetic causes: Diversity in body form is associated with duplication and variation in the spatial and temporal expression of Hox genes
20
Q

What was interesting about the body plans observed in the fauna in the Burgess shale?

A

Many of the body plans are not present today
- Gould argued that given a change to “rewind the tape of life” and play it again that we might se quite different animal forms today

21
Q

What do many Cambrian animals represent?

A
  • Now extinct “experiments” in animal form
  • In last half-billion years, animal evolution has mainly generated new variations of “old designs” - one of the main themes of evolution
22
Q

What is one way that Zoologists sometimes categorize animals according to?

A

By body plan, a set of morphological and developmental traits

23
Q

What is a grade?

A
  • A group whose members share key biological features
  • A grade is not necessarily a clade (a monophyletic group that includes an ancestral species and all of its descendants)
24
Q

Symmetry

A
  • Animals can be categorized according to the symmetry of the bodies, or lack of it
  • In general, symmetry firs lifestyle
  • Animals either have radial symmetry or bilateral symmetry - both present in fossil record for 550 million years
25
Q

Radial symmetry

A
  • Most are either sessile or planktonic (drifting)
  • Symmetry allows them to meet environment well from all sides
26
Q

Bilateral (two-sided) symmetry

A
  • Typically move actively from place to place coordinated by a central nervous system (CNS)
  • A dorsal (top) side and a ventral (bottom) side
  • A right and left side
  • Anterior (head) and posterior (tail) ends
  • Cephalization, the development of heads
27
Q

What is another way that animal body plans can vary by?

A

They can vary according to the organization of the animal’s tissues
- Tissues are collections of specialized cells isolated from other tissues by membranous layers
- During development, two or three germ layers give rise to the tissues and organs of the animal embryo

28
Q

Germ layers

A
  • The primary cell layers, formed in the earliest stages of embryonic development
  • During development, two or three germ layers give rise to the tissues and organs of the animal embryo
29
Q

Radiata

A
  • Have two germ layer (diploblastic)
  • Ectoderm, skin and central nervous system
  • Endoderm lines the digestive tract and gives rise to organs, such as liver and lungs
30
Q

Bilateria

A
  • Have three germ layers (triploblastic)
  • Mesoderm lies between the endoderm and ectoderm and develops into muscles and other organs between digestive tube and surface
31
Q

What is one reason that tumors can arise?

A

They can arise due to mistakes in gem layer differentiation
- teratomas are most common type and frequently derived from ectoderm

32
Q

True body cavities

A
  • Coelomates have a true coelom, a fluid-filled body cavity completely lined by mesoderm
  • Tissues surrounding cavity connect dorsally and ventrally to form mesenteries, which suspend internal organs
33
Q

Faux Body Cavities

A
  • I pseudocoelomates (Phyla Rotifera, Nematoda), a cavity incompletely lined by mesoderm and endoderm appears, the pseudocoelom
34
Q

No Body Cavities

A

Acoelomates (Phylum Platyhelminthes) have a solid body and lack a body cavity

35
Q

What is the function of the body cavity?

A
  • The coelomic fluid cushions the suspended organs, helping to prevent internal injury
  • In soft-bodied coeleomates, the non-compressible coelomic fluid can function as a hydrostatic skeleton against which muscles can work
  • The presence of a body cavity enables the internal organs to grow and move independently of the outer body wall
36
Q

Based on early development, many animals can be categorized as having what?

A
  • Protostome development or deuterostome development

Distinguished by differences in
- Cleavage
- Coelom formation
- Fate of the blastopore

37
Q

Coelom Formation

A
  • In protostome development, the splitting of solid masses of mesoderm forms the coelom
  • In deuterostome development, the mesoderm buds from the wall of the archenteron to form the coelom
38
Q

Fate of the Blastopore

A
  • In protostome development the blastopore becomes the mouth
  • In deuterostome development the blastopore becomes the anus
39
Q

What is the past hypothesis of animal phylogeny?

A
  • It is based mainly on morphological and developmental comparisons
  • Based on body plans & embryonic development
  • Each major branch is a grade of body-plan features shared by the taxa belonging to that branch
40
Q

What is the current hypothesis of animal phylogeny?

A
  • It is based mainly on molecular data
  • Based on nucleotide sequences of small subunit ribosomal RNA
41
Q

Points of agreement

A
  • All animals share a common ancestor
  • Sponges are basal animals
  • Eumetazoa is a clade of animals with true tissues
  • Most animal phyla belong to the clade Bilateria
  • Chordates and some other phyla belong to the clade Deuterostomia
42
Q

Points of disagreement

A
  • Morphology-based phylogeny indicates two bilaterian clades: deuterostomes and protostomes
  • Assumes that these modes reflect a phylogenetic pattern
  • Arthropods and annelids are grouped because have segmented bodies
43
Q

Ecdysozoa

A
  • The Ecdysozoa (nematodes, arthropods, and other phyla) secrete external skeletons (exoskeletons) (in nematodes the exoskeleton is called the cuticle
  • To grow the animal must molt the old exoskeleton and secrete a new, larger one, a process called ecdysis
  • While named for this process, the clade is actually defined mainly by molecular evidence

General Biology: OrganismL Biology and Evolution - Set 1 (23 decks)

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