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BIO916 2 > Sören - Annelids and molluscs > Flashcards

Sören - Annelids and molluscs Flashcards

1
Q

Concept: coelom

A

A cavity where the organs are. Present in all but “simple animals”

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2
Q

Concept: segmentation

A

The animal consists of multiple, similarly arranged segments along the body. Segments are rarely identical in more “advanced” forms (vertebrates are segmented, like the ribs).

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3
Q

Annelids subgroups

A

Polychaete: havsborstmaskar
Oligochaeta: fårborstmaskar
Leeches: iglar

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4
Q

Annelids structure

A

They are worms. Segmented, each segment has an isolated coelom. Generally stiff bristles made of chitin on each segment.

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5
Q

Polychaeta structure

A

Generally many bristles. Sometimes leglike extensions on each segment.

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6
Q

Oligochaeta structure

A

Fewer bristles than polychaeta. Never leg-like extensions on the segments.

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7
Q

Leeches structure

A

They lack bristles. Reduced segmentation (there may be visible rings, but they do not correspond to segments).

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8
Q

Polychaeta food

A

They may be:
- active hunters
- sedetary suspension feeders
- relying on symbiotic chemosynthetic bacteria
- deposit feeders

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9
Q

Oligochaeta food

A

Most are deposit feeders. A few are predators.

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10
Q

Leeches food

A

Many are predators. Many are ectoparasites (and suck blood).

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11
Q

Annelids digestion

A

Complete digestive system: anus is present, and food is digested in stomach and absorbed in intestines.

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12
Q

Polychaetes life cycle

A

Seperate sexes.
Temporary gonads initially release gametes to coelom.
Gonads released through excretion organs, through dedicated gonopores or through rupture of skin.
Nearly always ciliated larvae.
Asexual reproduction is rare.

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13
Q

Polychaetes planktonic reproductive stage

A

Many benthic forms transform to planktonic forms for reproduction. Either the entire individual transforms, or planktonic worms are budded off.

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14
Q

Oligochaetes and leeches life cycle

A

Hermaphrodites.
Permanent, distinct gonads.
Mating. Mutual fertilization.
Internal fertilization.
No larvae.
Eggs deposited in cocoon.
Asexual reproduction common.

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15
Q

Annelids swimming

A

Found in all three subgroups. Swimming with lateral muscular waves.

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16
Q

Annelids leg-like walking

A

Found in many polychaetes. Sideways contractions (somewhat like swimming) and leg-like extensions that attach to the substrate.

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17
Q

Annelids earthworm-like walking

A

Found in many polychaetes and all oligochaetes. Wavelike contractions of segments. Attaches to substrate with bristles. Made much easier by individual coelom in each segment.

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18
Q

Leeches walking

A

Walking like inchworms. They rely on two suckers, one in the front and one in the back. One sucker is always attached to the substrate.

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19
Q

Annelids circulatory system

A

A combination of distinct vessels and coelom. Often distinct gills, particularly in sedementary species. Often oxygen carrier, eg hemoglobin.

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20
Q

Annelids excretion

A

Well-developed excretion system. Often distinct for each segment. Exit pore on the body. Aquatic species excrete ammonia, terrestrial species excrete ammonia and urea.

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21
Q

Annelids nervous system

A

Generally well-developed brain and nervous system. Eyes and statocyst are well-developed in active polychaetes, reduced in many other groups, such as earthworms. Forms without distinct eyes may still have light receptors scattered across the body. Giant axons are generally present.

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22
Q

Polychaetes diversity

A

About 10000 species. Nearly always marine, a few species in freshwater. Paraphyletic. Generally many bristles. Temporary gonads.

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23
Q

Oligochaeta diversity

A

About 10000 species. The majority live in freshwater or are terrestrial. Paraphyletic. Few bristles. Permanent gonads.

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24
Q

Leeches diversity

A

About 700 species. The majority live in freshwater, some are terrestrial or marine. No bristles. Permanent gonads. Limited segmentation.

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25
Q

Mollusca subgroups

A

Gastropoda: snäckor
Cephalopoda: bläckfiskar
Bivalvia: musslor

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26
Q

Mollusca traits mantle

A

A layer of skin on the upper surface of the body. Often has an inner fold or cavity. Secretes a protective shell (made of calcium carbonate and protein) in most groups. Shell has been lost in many groups.

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27
Q

Mollusca trait foot

A

A muscular part on the opposite side of the mantle. Effectively always used for movement.

28
Q

Mollusca traits radula

A

Generally and extendable tongue. Covered by sandpaper-like teeth made of kitin.

29
Q

Gastropoda generellt

A

Marine, freshwater and terrestrial. About 75000 species.

30
Q

Gastropoda structure: torsion

A

The ancestor of all gastropoda had torsion: a 180 degree rotation of all intestines and a lot of organs. Some groups secondarily partially “detorsion”.

31
Q

Gastropoda structure: coiling

A

The ancestor of all gastropoda had coiling. All individuals of a species are coiled the same way. Most species coil to the right (when the tip points up, the mouth is on the right). Many groups independantly evolved left-coiling or uncoiled.

32
Q

Gastropoda food

A

Very variable: plants, algae, scavengers, carnivores, sediment feeders, suspension feeders. Nearly always scrape of food with radula. All have a complete digestive system. All have large blind sacs called digestive glands.

33
Q

Gastropoda cnidocyst uptake

A

Some snails feed on cnidaria. They take up cnidocysts and move them to specific organs where they are used for defense.

34
Q

Gastropoda chloroplast uptake

A

Some feed on algae and take up chloroplasts. These live and photosynthesize inside the slug, but cannot reproduce.

35
Q

Gastropoda sex and mating

A

Aquatic species often have distinct sexes or are protandry hermaphrodites.
Land snails are simultaneous hermaphrodites.
Nearly always internal fertilization, land snails also simultaneous.
Mating is only possible if they are coiled the same way.

36
Q

Concept: benefits of larvae

A

Banthic (especially sessile) animals are bad at dispersing, and generally live in good places.
Planktonic larvae can disperse, but may land at a bad place. Therefore it is good with moving larvae.
More common in marine systems, because water balance is difficult when you are tiny.

37
Q

Gastropoda life cycle

A

No larvae in terrestrial or freshwater species.
Potentially long larval stage in some marine forms.
First larval stage (when present) is very similar to annelid larvae.
Many species have long-lived, feeding planktonic larvae.

38
Q

Gastropoda movement

A

Most move with cilia and muscles on the foot.
The foot often secretes mucus to make movement easier.
The foot works as a suction cup for some species.
A few marine, shell-less snails can swim using extensions of the foot.

39
Q

Gills vs lungs structure

A

Gills: very thin, big parts of the surface is in contact with a lot of water.
Lungs: somewhat thicker, surface is in contact with a lot of air.

40
Q

Gastropoda air uptake

A

“Primitive forms” have gills in their mantle cavity.
Land snails have transformed the mantle cavity to lungs.
Most snails have lost one lung/gill.
Some marine forms have lost their mantle gill, and have gills elsewhere or take up oxygen via the skin.

41
Q

Gastropoda organs

A

Well developed heart, but no capillaries.Blood flows freely in coelom.
Often oxygen carrier.
Well-developed kidneys, often just one.
Land snails excrete uric acid.

42
Q

Gastropoda: nervous system and sensory organs

A

Well-developed head with brain.
Giant axons normally present.
Eyes present, sometimes small eye spots, sometimes well-developed with lenses.
Tentacles (land snails have eyes on one pair)
Statocyst on foot.

43
Q

Gastropoda siphon

A

Many have a fold in the mantle called siphon. Used by some predators to hunt: water is sucked in, receptors inside mantle smells the water.
Some freshwater species use it as a snorkel.

44
Q

Cephalopoda generellt

A

About 650 species. Exclusively marine.

45
Q

Cephalopoda structure ink

A

Present in nearly all cephalopods.
A gland is attached to intestines, the ink is discharged in anus.
Mainly defense, sometimes used for hunting.

46
Q

Cephalopoda food

A

All are carnivores.
Food is captured with tentacles (modified parts of the foot).
Hard “beak” of chitin is used to break up food parts.
Radula present, but not extendable outside of the mouth.
Complete digestive system and large blind sacs called digestive glands.

47
Q

Cephalopoda tentacles

A

Nautilus: 100 tentacles without suction cups.
Octopodiformes: 8 arms with suction cup all over it.
Decapodiformes/squids: 8 arms with suction cups all over is, 2 long tentacles with suction cups at the ends, very fast tentacles to capture prey.

48
Q

Cephalopoda life cycle

A

Always seperate sexes.
Spermatophores released to mantle. Modifies arm is used to transfer it to the female gonopore.
No larvae, but some benthic species have a panktonic stage for dispersal.

49
Q

Cephalopoda movement siphon

A

Water enters at the edges of the mantle, mantle is closed, water is pumped out of the siphon.
The siphon is movable, so they can swim in any direction.
“Fins”, extended part of the mantle, help with stability.

50
Q

Cephalopoda movement shell

A

Those with shell can regulate buoyancy by pumping air in or out of the shell.
Very important for nautilus.
Semi important for cuttlefish and many other decapodiformes.

51
Q

Cephalopoda movement arms

A

Many octopuses mainly move by “walking” with their arms. Also allows movement on land.

52
Q

Cephalopoda organs

A

Paired gill in mantle. Water is constantly pumped into the mantle (for movement), which brings a lot of oxygen to the gills.
Kidneys similar to other molluscs.

53
Q

Cephalopoda circulation system

A

A completely closed circulatory system.
An additional pair of hearts at the base of the gills.
Generally oxygen carrier.

54
Q

Cephalopoda nervous system

A

Large central brain.
Largest known giant axon.
Large mini brains at the base of each arm.

55
Q

Cephalopoda sensory organs

A

Well-developed statocyst that respond to sound, but the brain does not, potentially deaf as protection against whale sonar.
Nautilus have simple eyes. All other have complex, image forming eyes with lenses. Lenses are kept perfectly horizontal by statocyst. Eyes focuses by moving lense.

56
Q

Diversity nautilus

A

About 6 species. Only cephalopod with external shell.

57
Q

Diversity octopusses

A

About 300 species. 8 arms. Shell completely lost.

58
Q

Diversity decapodiformes

A

About 350 species. 8 arms + 2 tentacles. Generally internal remnants of shell.

59
Q

Bivalvia generellt

A

Diverse in marine and freshwater systems. About 30 000 species.

60
Q

Bivalvia structure

A

Two shells. Very large mantle cavity. Lost radula.

61
Q

Bivalvia food

A

Effectively all have a complete digestive system and large blind sacs.
Primitive forms are sediment feeders.
Few rely on chemosynthetic or photosynthetic symbionts.
Very few (shipworms) live on wood which they slowly burrow through.

62
Q

Bivalvia filter feeders

A

Water is sucked into the mantle through one opening. Food is captures in enlarged gills, moved by cilia to mouth. Water is pumped out through another opening.
Burying forms have two siphons to ensure one direction of water flow.

63
Q

Bivalvia life cycle

A

Adults are benthic.
Sexes normally seperate.
External fertiization.
Planktonic larval stages.
Many freshwater species are ectoparasites on fish as juveniles.

64
Q

Bivalvia movement

A

Adults generally sessile. Often attached to substrate with collagen threads. Some species burrow into the sand, or move a little with their foot. A few species (scallops) can swim by opening and closing the shell.

65
Q

Bivalvia organs

A

Circulatory, gas uptake and excretion are similar to gastropods.
Paired kidneys and paired gills.

66
Q

Bivalvia nervous system

A

No distinct head or brain. Statocyst present. Distinct eyes generallt absent, although present in scallops. Many species are light-sensitive despite lacking distinct multicellular eyes.

BIO916 2 (3 decks)

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