Transcript Arthropods - Claremont Colleges

Animal Adaptations
Arthropods
Biological Control (Integrated
Pest Management)
Animal Adaptations
Correlations of life choices with
structural and physiological
changes. Things to think about
Why choose?
= competition – or avoiding it.
Reproductive cycles
• All adults are diploid – haploid cells are
egg and sperm only.
• Egg almost always bigger (heterogamy)
• Primitive – both egg and sperm released
for external fertilization
• Advanced – egg retained, sperm released
• The fertilized egg (outside body) or a
structure to produce eggs and sperm can
be dispersal phase.
Coral life cycle. The medusa (like a jellyfish) is diploid, but male or female
or both. Meiosis in it produces eggs and sperm – planula is a dispersal
phase
Issues with reproduction (for each choice- what are the pros and cons.)
1. How many young?? (How many needed??)
2. Size of eggs?
3. Altricial vs precocial
4. Parental care
5. Retain egg in mother until hatching.
What affects the choices?
• R vs K species – life span
• Life history – are parents around??
Sessile vs motile?
Which systems affected?
What limits placed on where
you live- why?
Sessile living: sponge, corals,
Reproduction: sexual, motile sperm find egg, but also cloning (asexual)
plus
regeneration
Food; in water, mostly ocean (why?)
Dispersal: larvae with flagella.
Protection: regeneration, spicules
Symmetry: assymetric vs
radial, bilateral
Which leads to what systems?
Nerves and senses and
brain concentration.
One of the major senses: Light sensitivity
Nearly all cells have it – goes back to bacteria.
Higher animals – special light sensory devices – function
detect light – use for clocks – telling seasons, etc.
detect movement only - protection
identify shape; - leads to memory.
How to take an image – break it into bits of information – transmit to brain for
storage and processing?
Note: diurnal vs nocturnal
diurnal ; shape perception = eyes
nocturnal: -vision – see movement, not shape.
shape perception in dark = radar, sonar – bats and porpoises
What if you are motile and can’t find a mate?
Under what conditions is this likely to occur??
Parasites in body
Whiptail lizards, among others
Parthenogenesis = egg develops without
fertilization.
Why here? (are males that repulsive?)
Multicellularity - size
What systems required to gain in size? Why?
Circulation, respiration, excretion, skeleton
Skeleton – a requirement of size
External
Internal
Hydrostatic
Limitations of each?
Hydrostatic
Muscles compress
compartments – push the
worm forward. Setae(spines)
hold portions of body to
ground.
Note cross – sectional diameter.
respiration
Aquatic
• Through skin if small
• Gills if bigger (large surface area in water)
Terrestrial
keep wet gills
lungs
insects – spiracles.
Large surface area in contact with
environment – skin respiration
Crab gills – feathery
under surface for
protection
Fish gill structure – large surface area
Terrestrial vs aquatic:
Which systems affected?
As with plants.
How to avoid drying out
How to breathe – get
oxygen.
Feeding types:
Filter feeder
Herbivore
Carnivore
Omnivore
Specialized food; molluscs, fish, ants,
Which feeding type leads to:
more active life?
being clever?
larger population size?
Cold vs warm blooded: - what are
the advantages, disadvantages of
each?
What conditions might favor the
development of warm
bloodedness?
Figure 40.9 Ectotherms and Endotherms React Differently to Environmental Temperatures (A)
Mammals as
maxitherms.
How to deal with harsh conditions?
Like a plant: - survive as egg (seed)
- adapt (fur, evaporative cooling, etc)
New means:
-migration – avoid bad conditions
-hibernation
Allen’s rule; larger extremities in warmer climates
Arthropods
beetles
Butterflies and
moths
Bees, ants, wasps
Trilobites – stem group, marine
External skeleton
Metamorphosis vs incomplete
metamorphosis.
Why insects so successful?
• r species – adaptable
• extreme specialists
• live in water, land and air
• flight
• excellent nervous systems
• life cycle; larval feeding.
• all food types, plant, animal, scavenger, predator, etc.
• many have social behavior
Insects as pests
• diseases – carriers of
protozoa, bacteria
• crop pests – direct
effects or carriers of
fungi, etc.
How to deal with insects
• Pesticide -Insecticide: a chemical that kills
all insects, but they develop resistence,
and some like DDT harm other organisms
• Biological control: Know your enemy and
find a chink in their life cycle; four
examples. Problem – kills only the target
insect.
Find a natural parasite or disease of the pest.
Breed it, and release it into the environment
Here parasitic wasps lay eggs on caterpillars, kill them so they won’t eat a
crop.
Screw worm fly
Screw worm eradication
• Females only mate once
• Can’t tell difference between sterile and
fertile males
• Can sterilize with radiation
So: knock the population down with pesticide
release a lot of sterile males 10-100 for each fertile male
get rid of flies in one year.
prevent reintroduction
Moth and caterpillar crop
pests
Females release a
pheromone to
attract males.
Synthesize the
pheromone
Place in traps
around the crop
Poor female left
forlorn in the field.
Life cycle – juvenile hormone
absence allows pupa formation.
So synthesize the juvenile
hormone, spray on crop
Caterpillers never
metamorphoze, never pupate.
No adults formed, no increase
in population.
Integrated Pest Management
• Use a pesticide to knock down the insect
population
• Use a biological control to finish it off.
New technique – Bt corn etc.
Insert the genes for a bacterial toxin into a plant crop (plus the genes to turn
it on, etc.
Bt is a bacterial toxin against moth and butterfly caterpillers.
To kill a susceptible insect, a part of the plant that contains the Bt protein (not
all parts of the plant necessarily contain the protein in equal concentrations)
must be ingested. Within minutes, the protein binds to the gut wall and the
insect stops feeding. Within hours, the gut wall breaks down and normal gut
bacteria invade the body cavity. The insect dies of septicemia as bacteria
multiply in the blood. Even among Lepidoptera larvae, species differ in
sensitivity to the Bt protein.
Why are biological controls good?
• kill pest species only
• pest cannot develop resistence to them
• no chemical residue in water supply, etc.
So why are chemical pesticides overwhelmingly preferred??
By Farmer:
• don’t need to know your enemy – just spread the chemical
• chemical kills any and all pests immediately – no lag time.
• often relatively cheap (why? See below)
By the Industry (Dow and Monsanto Chemical)
• bigger market; works on any crop
• can patent the product (unique chemical created by company
• If resistence, make a new chemical (planned obsolescence)
•Result: only crops that are big (corn) might use biological controls
• not used for small volume crops or in undeveloped countries
• government must subsidize development.