reproduction & biogeography

Question 1

definition of reproduction

Answer 1

Replication of individuals (required for population maintenance/growth)

Question 2

definition of dispersal

Answer 2

Geographical spread of progeny

Question 3

definition of migration

Answer 3

Directed movement to a different location

Question 4

what’s the reproductive strategies

Answer 4

asexual vs sexual
gonochorism vs hermaphroditism

Question 5

what’s the fertilisation strategies

Answer 5

broadcast spawning
copulation

Question 6

what’s the larval strategy

Answer 6

associate energy with number of larvae

Question 7

name asexual reproduction strategies and what organisms do it

Answer 7

• Asexual reproduction in salps and doliolids
• Fission in polychaetes and echinoderms
• Fragmentation in corals
• Budding in colonial invertebrates (corals, ascidians, etc.)
• Budding in solitary cnidarians (anemones)
• Strobilation in scyphozoans

Question 8

when is asexual reproduction beneficial

Answer 8

under favourable conditions; where mates are hard to find or (in colonial forms) where size confers an advantage (e.g. stronger feeding currents, resistance to predation)* - requires less energy

Question 9

what is Hermaphroditism

Answer 9

Both male and female reproductive organs

Question 10

what are the 2 different types of Hermaphroditism

Answer 10

Sequential hermaphrodites
- Start as one sex, changes to another e.g. slipper limpet
Simultaneous hermaphrodites
- Possesses both reproductive organs at the same time
- Self-fertilisation rare, however but any two organisms of the same species can mate with each other e.g. barnacles

Question 11

what kind of method does sexual reproduction require

Answer 11

method of sperm transferral - living in seawater allows the simple shedding of sperm and eggs into the water column
- Planktonic gamete production is often synchronous (tied to tidal or lunar cycles)
- Special chemical mechanisms for gamete recognition

Question 12

what ensures successful sperm transferral

Answer 12

Direct contact or copulation
- Physical factors (distance, turbulence) will affect fertilisation success

Question 13

what is brooding

Answer 13

Fertilisation from copulation, or inhalation of sperm
- Eggs and sometimes larvae are retained - larvae released are comparatively more developed
- For example, decapod larvae undergo the nauplius stage within the egg, hatching as more developed zoea

Question 14

3 reasons why the Vast majority of planktonic larvae will die

Answer 14

• swept into inhospitable habitats
• predation
• Starvation

Question 15

what’s the 3 larval strategies

Answer 15

1. Direct release
2. Dispersal over a short distance (relatively short- lived, lecithotrophic larvae)
3. Dispersal over a long distance (longer-lived, planktotrophic larvae)

Question 16

explain the direct release larval strategy

Answer 16

• Larvae released next to adults: NO PLANKTONIC STAGE
• Many species viviparous, or brood larvae, producing juveniles as miniature adults
• Littorina saxatilis - broods fertilised eggs and releases fully-formed (but very small) snails
• Nucella lapillus = oviparous – eggs are cemented to the substrate and hatch as miniature adults

Question 17

what are lecithotrophic larvae

Answer 17

• Larvae that depend upon a yolk for nutrition (relatively large egg)
• Larvae have no feeding or digestive structures
• Capable of limited swimming – few hours to a day in the water column
• Short dispersal – 100s metres at most
  e.g. tadpole larvae of tunicates

Question 18

what are planktotrophic larvae

Answer 18

• Feed whilst they are in the plankton
• Feed on planktonic bacteria, phytoplankton, smaller zooplankton
• Planktonic stage can last several months
• Much greater capacity for dispersal over a long distance
• Often, development progresses through a series of stages (e.g. crustacean zoea and megalops stages)
• Particularly long lived larvae can cover very long distances: Teleplanic larvae

Question 19

what are the two important risks Planktonic larval stages come with

Answer 19

1. Predation
2. Finding a suitable settlement site
   - Some planktotrophic larvae (e.g. Mytlius edulis) can delay metamorphosis until a suitable site is located

Question 20

Planktotrophic larvae characteristics

Answer 20

• they are in the plankton for longer, so there is a balance between dispersal, energy investment and survival
• For planktotrophs, timing is everything - In British waters, spawning is often timed to take advantage of the spring phytoplankton bloom
• Planktonic larvae = rare at high latitudes

Question 21

what’s the Position in water collum of Planktotrophic larvae

Answer 21

• Larvae will go through one or more stages of photopositive and photonegative behaviour
• Larvae can show behavioural (depth) changes to take advantages of local currents and tides
• Water = very hard to move through when small – produce monofilaments to reduce drag

Question 22

what is photopositive and photonegative behaviour

Answer 22

Photopositive – near surface
Photonegative – close to bottom

Question 23

how do Planktotrophic larvae settle

Answer 23

• Larvae use chemical and mechanical cues to select an appropriate substrate
• Some show gregarious settlement
• SIPC – Settlement-inducing protein complex

Question 24

what are the Advantages of planktonic larvae

Answer 24

• Species with planktonic larvae generally occur over greater geographical ranges than those without
• Avoiding over-crowding
• Taking advantage of new habitats
• Marine ecosystems are not stable (even in the deep sea)
• Larval spillover from protected areas

Question 25

what is The fundamental limit on species’ distribution

Answer 25

physiology (also evolutionary history - shown by invasive species)
- The continental shelf is a significant barrier
- Also: currents, major river outflows, land masses