Topic 1

Question 1

Main principles in Zoology

Answer 1

• Evolution
  - Reproduction and development
  - Behavior
  - Movement
  - Nutrition
  - Match between Structure and Function
  - Match to the Habitat

Question 2

Taxonomic levels

Answer 2

1 - Kingdom  -    ממלכה
2- Phylum     -    מערכת
3- Class        -    מחלקה
4- Order       -       סדרה
5- Family      -   משפחה
6- Genus      -          סוג
7- Species    -          מין

Question 3

Typological definition of species

Answer 3

• Based on morphology - if they’re physically similar we say that this group of organisms belong to the same species, genus…
• Every species has their “type specimen” (מייצג למין) - individual organism from which the species was originally defined.

Question 4

Biologic definition of species

Answer 4

“Reproductive community of populations (REPRODUCTIVELY ISOLATED FROM OTHERS) that occupies a specific niche in nature”

Key points:

• Shared ancestor (אב קדמון משותף)
• Reproductive isolation (הפרדה רבייתית)
• Shared ecological characteristics (נישה אקולוגי)

Problematic points:

• Reproductive isolation in the species that got extinct (נכחדו)
• Species that reproduce asexually
• level of reproductive isolation (there are places where it isn’t absolute)

The problem with this definition is that it’s not possible to know if they’re reproductively isolated other than by breeding them.
The biological definition of Species is theoretically completely correct, but in practicality is not enough to classify all organisms.

Question 5

Evolutionary definition of species

Answer 5

“a single lineage of ancestor-descendant populations that maintains its identity from other such lineages and that has its own evolutionary tendencies…”

Key points:

• shared common ancestor
• separate evolutionary history
• one genetic unit??? (סחיפה גנטית וסלקציה)

(Implication: if two groups have different evolutionary history, were exposed to different selective forces, then they’re considered as two separate species (evolutionary definition) even if they’re able to have fertile offspring and would be considered as one species biologically)

Question 6

Phylogenetic Definition of species

Answer 6

“irreducible grouping of organisms distinct from other such groupings, with parental pattern of ancestry and descent”

Key points:

• shared common ancestor
• the smallest possible group that underwent evolutionary change separately
• one population without branching outs (התפצלויות) in the phylogenetic tree
• there is no התייחסות to evolutionary processes**

Question 7

Systematica

Answer 7

Study of the variety of living organisms (alive and extinct)/(נוכחי ונכחד) and their relations in time: Taxonomia(naming of organisms) + Phylogenesis(building of evolutionary relations between organisms) + Evolutionary Processes (genetic variability, genetic drift (סחיפה גנטית), selection and reproductive isolation)

Question 8

Paraphyletic Group

Answer 8

Group of taxons that contains the shared ancestor but not all of it’s descendants

Question 9

Polyphyletic Group

Answer 9

Group that contains taxons that are distant from each other and doesn’t contain the shared common ancestor

Question 10

Polytomy

Answer 10

Unresolved pattern of divergence: when it’s known that several species are coming from an ancestor but there isn’t enough information to know the correct branchings

Question 11

Sexual Reproduction in Sponges

Answer 11

Hermaphrodites. Life cycle: secretion of sperm cells-production of ovules-filtering of sperm-formation of zygote->embryo->larva - larva goes out and settles in new place - larva metamorphosis into young sponge.

Question 12

Main Characteristics of Sponges

Answer 12

1. Belong to Metazoa (pluricellular organisms with Blastula stage in embryonic development)
2. Simplest body (organizationally) - no muscles, no nerves, no tissues
3. With only a few types of cells within an extracellular matrix (מטריצה חוץ תאית) and a skeletal element in the shape of needles
4. Most of them live in the sea though some also in sweet water
5. They are believed to have evolved from Choanoflagellates (unicellular organisms with a flagellum (שוטון))
6. Every different sponge cell type is specialized in a specific function and they’re all held together by an organic material secreted from the cells

Question 13

Osculum*

Answer 13

Opening for the exit of the water (פתח)

Question 14

Choanocytes

Answer 14

Collar cells (תאי רביד)
- Cells in charge of the water flow inside through the canals and חללים of the sponge for nutrition and transport of oxygen and disposal of חומרי פסולת.
- Globular shape
- They have a flagellum (שוטון) that pushes the water outwards, surrounded on its base by a collar of microvilli that absorbs the nutrients
- The leftovers from what the choanocytes don’t need for their own nutrition, they pass on to the archaeocytes, and they break down this products into nutrients so that they can reach other cells.
If there are particles that are too big, then they transfer them onto the outer sponge parts and from there they’re secreted into the outside

Question 15

Pynacocytes

Answer 15

Flat cells anchored to the mesohyl in the outermost layer of the sponge, “dense”, pressed against one another, and the constitute the external layer of the sponge, which is called Pinacoderm.

• Phagocytosis: Absorb nutrients and small molecules
• Contraction: limited contraction ability in cellular level, if all the cells do it together then the sponge can contract as a whole.

Question 16

Porocytes

Answer 16

Type of cell that are in the sponge Pinacoderm layer, they are hollow, like a canal, where the water goes through.
Ostium(singular)/ostia (plural) - is the name given to the wholes in the pinacoderm (פתחים)

Question 17

Archaeocyte

Answer 17

• Located inside the matrix of the mesohyl,
• have ameboid shape,
• functions:
  
  • property of being able to become any other of the cell types,
  • digestion of nutrients
  • disposal of strange bodies (גופים זרים) (immune protection?) taken from the water
  • building of the skeleton
  • reproduction
  • החלפת תאים?

Question 18

Mesenchyme* (mesohyl)

Answer 18

Gelatinous matrix surrounding sponge cells; area with extracellular fluid that binds all the structure together, =mesoglea, =mesenchyme.

Question 19

Spongocel*

Answer 19

Space inside of the sponge

Question 20

Two types of Skeleton in Sponges

Answer 20

Skeletal skeleton (שלד מחטני) & Organic Skeleton
There isn't a significant movement, serves mostly for protection (from predators) and shape.

Question 21

Skeletal Skeleton (שלד מחטני)

Answer 21

Spicules* (מחטונים) - inside the mesohyl, formed by specialized archaeocytes. Classification of Sponges according to shape and material of spicules.

Question 22

Organic Skeleton

Answer 22

Spongin

• type of collagen.
• Secreted by archaeocytes.
• Forms network of fibers.
• Helps keep the shape of canals and חללים

Question 23

Three Types of Sponges

Answer 23

Asconoid, Syconoid, Leuconoid. (אסקון, סיקון, לאויקון)

• Increasing organizational complexity - as the surface area increases, also increases the efficiency
• Sponges are built for the pumping (שאיבה) and filtering of water through the body - unidirectional, nonstop flow of water

Question 24

Asconoid (אסקון)

Answer 24

The water goes inside from the outmost layer and goes out from the opening, this is the simplest type. The size is about a few millimeters of absorbing surface, this means that the surface area is not very big.

Question 25

Syconoid (סיקון)

Answer 25

In order to maximize the absorption of nutrients, they having bends. Here the water goes through the channels in the outer part, then through the channels in the choanocytes and there isn't a lot of area there, and then they go into the big sponge space (spongocoel)

Question 26

Leuconoid (לאויקון)

Answer 26

It is full of a series of channels/rooms that maximize the surface area and minimize the area through which the water can go through, this a very complex structure in comparison, that allows for a considerable increase in efficiency for obtaining nutrients through water filtering

Question 27

Ecologic importance of sponges

Answer 27

Filtering of the water: can extract bacterias from the water and use for their nutrition, also from other particles

Question 28

Regeneration of sponges

Answer 28

The Archaeocytes have the ability to become any other type of cell in the sponge, they have a very high capacity for regeneration, even being able to regenerate missing parts in the body. One small piece of sponge will grow to be a full sponge (external budding). (Method utilized by sponge cultivators/sellers). Also, if all the cells of the sponge were to be disseminated and then put back together, the sponge will be recreated, meaning they have aggregation capability.

Question 29

Type(s) of reproduction in Sponges

Answer 29

Sexual & Asexual - (Larva & Budding)

Question 30

Asexual Reproduction in Sponges

Answer 30

Budding (הנצה): - Does not involve formation of gametes. - Two types: internal & external Budding - External budding: when a portion of the sponge breaks off and then regenerates into a complete organism. - Internal budding: Internal budding takes place by the formation of internal buds called gemmules (small collection of several different types of cells that are enclosed by a protective covering.).

Question 31

Sexual Reproduction in Sponges

Answer 31

Hermaphrodites. Life cycle: secretion of sperm cells-production of ovules-filtering of sperm-formation of zygote->embryo->larva - larva goes out and settles in new place - larva metamorphosis into young sponge.

Question 32

Gemmule

Answer 32

Gemmules are a small collection of several different types of cells that are enclosed by a protective covering. Mainly archaeocytes (full of חומרי מזון & surrounded by ameboids?) that secret a resistant protective cover (מעטה) which contains מחטי שלד. This is an important survival mechanism in unfavorable conditions where the adult may not survive. The protected gemmule can withstand harsh conditions like יובש and can begin to develop into an adult sponge when conditions are more favorable.

Question 33

Graph of width of section area vs. velocity of water

Answer 33

What we can see in this graph is that the more we go inside into the interior of the sponge, the surface area increases, and with its increase, the speed of the water decreases. The surface area is maximum at the Choanocyte (C) and there the speed is super slow (10 microns per second), and the speed of the water is maximum at the opening of the "exhalant canal" (where the water goes out from into the spongocoel) *** The water flow is fastest on the exit, this pushes the water that has already been filtered away from the sponge and allows the new water to get closer to the sponge and for it to be filtered by the sponge and continue the cycle…

Question 34

Phylogenetic trees

Answer 34

- nodes (נקודות התפצלות) - it gives information of relations, not of time - Sister taxa: when two taxons are very close to one another (it can be sister species/genus)

Question 35

Symmetry in Sponges

Answer 35

no symmetry

Question 36

Body layers in sponges

Answer 36

they have no body layers and no gastro-vascular cavity. The larva is like a Blastula. (They don't undergo gastrulation)