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INVERTEBRATES Flashcards

YOKO NA LORD (48 cards)

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1
Q

What is a key milestone in life’s history that allowed complex organisms to develop from single-celled ancestors?

A

The evolution of multicellularity

This transition has occurred independently in various lineages, each taking unique evolutionary paths.

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2
Q

How many independent occurrences of multicellularity are estimated to have arisen in various eukaryotic groups?

A

Estimates range from 13 to 25 occurrences

This is based on different definitions.

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3
Q

Which six major eukaryotic clades have formed complex multicellular organisms?

A
  • Animals
  • Fungi (especially symbiomycotan fungi)
  • Brown algae
  • Red algae
  • Green algae
  • Land plants
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4
Q

What are the two main pathways through which multicellularity emerges?

A
  • Clonal Aggregation
  • Non-Clonal Aggregation
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5
Q

What selective pressure drives the evolution of multicellularity related to defense?

A

Predation

Larger multicellular structures enhance defense against predators.

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6
Q

What is a significant experimental model for studying the evolution of multicellularity?

A

Yeast models (Saccharomyces cerevisiae)

These can form multicellular ‘snowflake’ clusters in the lab.

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7
Q

What is ectoderm?

A

One of three germ layers from which organs and tissues form

It is involved in the early embryonic life of all animals except sponges.

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8
Q

What is the role of mesoderm in triploblastic animals?

A

It gives rise to several tissues, including muscles and the vascular system

It interacts with endoderm and ectoderm during organogenesis.

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9
Q

What is the endoderm responsible for?

A

Forming the epithelium that lines the primitive gut

It develops into organs like the digestive tract, liver, pancreas, and lungs.

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10
Q

What evolutionary development allowed for the creation of internal organs in animals?

A

The evolution of the mesoderm

This led to more complex body structures and organ systems.

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11
Q

What defines bilateral symmetry in animals?

A

The concentration of nerve tissue in the head, allowing for a clear front and back

This feature enables coordinated movement.

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12
Q

What are the three categories of body cavities in triploblastic animals?

A
  • Acoelomates
  • Eucoelomates
  • Pseudocoelomates
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13
Q

What is acoelomates?

A

Triploblasts that do not develop a coelom

An example includes animals from the phylum Platyhelminthes (flatworms).

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14
Q

What is the defining feature of eucoelomates?

A

They have a true coelom lined with mesoderm

Examples include annelids, mollusks, and arthropods.

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15
Q

What is a pseudocoelom?

A

A body cavity arising from both the mesoderm and endoderm

An example includes roundworms (phylum Nematoda).

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16
Q

What is the enterocoel theory?

A

It proposes that the coelom arose from pouch-like structures in the embryonic archenteron wall

This theory was first introduced by Lankester in 1877.

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17
Q

What is the function of the coelom?

A
  • Shock absorber
  • Enhances flexibility of body organs
  • Hydrostatic skeleton aiding locomotion
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18
Q

What is a defining feature of metazoans?

A

The true coelom, a bodily cavity formed by the three germ layers

This cavity is fluid-filled and accommodates organs.

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19
Q

What are the three groups of the animal kingdom based on the nature of coelom?

A
  • Acoelomate
  • Pseudocoelomate
  • Coelomate
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20
Q

What is the definition of coelom?

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A

The fluid-filled body cavity present between the alimentary canal and the body wall.

21
Q

What type of animal lacks a true coelom?

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A

Pseudocoelomate

The body cavity is partially filled with mesodermal cells.

22
Q

What is the function of coelomic fluid in soft-bodied animals?

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A

Cushioning internal organs, providing a hydrostatic skeleton, aiding in locomotion, and distributing nutrients and waste products.

Coelomic fluid allows contracting muscles to exert pressure, leveraging fluid pressure for movement.

23
Q

What are coelomocyte cells?

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A

Cells that bolster the immune system by initiating humoral immune responses and phagocytosis.

They can be freely floating in the coelom or attached to its walls.

24
Q

What does a pseudocoelom refer to?

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A

A fluid-filled body cavity that is not fully lined by mesodermal tissue and is located between the mesoderm and endoderm.

It is derived from the blastocoel.

25
What is the evolutionary significance of the pseudocoelom?
It represents a milestone in animal body plans, contributing to greater complexity and enhanced mobility. ## Footnote It serves as an intermediate stage between acoelomates and coelomates.
26
Describe the two competing hypotheses of pseudocoelom evolution.
1. Coelomate to Pseudocoelomate Hypothesis: loss of true coelom. 2. Acoelomate to Pseudocoelomate Hypothesis: evolved from acoelomate ancestors retaining the blastocoel. ## Footnote Both hypotheses explain the evolutionary transition to pseudocoelomates.
27
What are examples of pseudocoelomates?
* Nematoda: Roundworms * Rotifera: Rotifers * Gastrotricha: Gastrotrichs * Nematomorpha: Horsehair worms * Kinorhyncha: Mud dragons ## Footnote Each group showcases unique features that define their classification.
28
What are the three major groups of deuterostomes?
* Echinoderms * Hemichordates * Chordates ## Footnote These groups show distinct evolutionary traits and adaptations.
29
What is the significance of the blastopore in deuterostome development?
It becomes the anus, with the mouth forming later in development. ## Footnote This distinguishes deuterostomes from protostomes.
30
What is radial cleavage in deuterostomes?
Embryo cells divide and stack neatly on top of each other. ## Footnote This is different from the spiral cleavage seen in protostomes.
31
What does indeterminate growth mean in the context of deuterostomes?
If a cell from the early embryo is separated, it can still grow into an entire organism. ## Footnote This characteristic is why identical twins can form in humans.
32
What is segmentation in biology?
Division of a body into repeated sections, aiding in locomotion, organ placement, and body organization. ## Footnote It is a fundamental concept in biology.
33
What are the types of segmentation?
* Morphological Segmentation * Developmental Segmentation * Evolutionary Segmentation ## Footnote Each type examines different aspects of segmented structures.
34
What is the significance of Drosophila in segmentation studies?
A landmark study that identified genetic controls over segmentation. ## Footnote It led to broader research in developmental biology.
35
What is the evolutionary implication of segmentation?
Segmentation has arisen independently in different lineages, showcasing genetic similarities and allowing specialization of body parts. ## Footnote This contributes to survival and evolutionary success.
36
What are jointed appendages?
Segmented limbs that assist in locomotion and other functions. ## Footnote They are crucial for the movement of species.
37
What subphylums are included in the Phylum Arthropoda?
* Chelicerata * Crustacea * Hexapoda * Myriapoda ## Footnote These subphylums represent diverse groups within arthropods.
38
What is the role of the exoskeleton in arthropods?
It supports and protects the animal's segmented body and jointed appendages. ## Footnote Made of chitin, the exoskeleton provides structural integrity.
39
What is the importance of fossil records in understanding arthropods?
They provide traces of evolutionary lineages and insights into the origin of jointed appendages. ## Footnote Fossils help reconstruct the evolutionary history of species.
40
What is the primary material that supports and protects the segmented body of arthropods?
Chitin ## Footnote Chitin is a long-chain polymer of N-acetylglucosamine, which is a derivative of glucose.
41
What are the functions of the jointed appendages in arthropods?
Functions include: * Movement (walking) * Grasping * Sensing * Defense * Eating * Mating ## Footnote Each appendage may have different specialized functions depending on the species.
42
When were the earliest arthropod-made trace fossils found?
During the Early Cambrian, roughly 537 million years ago. ## Footnote This indicates the long evolutionary history of arthropods.
43
Which group of arthropods is recognized as the first recorded?
Trilobites, recorded 521 million years ago. ## Footnote Trilobites are an extinct group of marine arthropods.
44
What role does the gene Distal-less (DII) play in arthropods?
It is crucial for forming limbs and proper segmental patterns in appendages. ## Footnote This gene is part of a complex network influencing appendage development.
45
What are lobopodians?
The earliest members of panarthropoda with simple unspecialized appendages. ## Footnote Lobopodians serve as a reference point for the evolution of more complex jointed limbs.
46
Which two groups are included in panarthropoda?
Tardigrades (water bears) and Onychophora (velvet worms). ## Footnote Both groups retain appendages that are closer to their ancestral lobopod form.
47
True or False: Appendages in arthropods have specialized functions that allow them to occupy various habitats.
True ## Footnote Arthropods can thrive in both aquatic and terrestrial environments due to their diverse appendage functions.
48
Fill in the blank: The earliest records of arthropod trace fossils were found during the _______.
Early Cambrian ## Footnote This era marks significant evolutionary developments in arthropods.

Evolutionary Biology (12 decks)

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