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Pests, Plagues & Politics Lecture 1 The Success of Insects. Key Points: The Success of Insects. Evidence of Success Numbers Longevity Diversity. Reasons for Success Physical size Flight Fecundity. Insects by most measures, are the single MOST successful animal group

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key points the success of insects
Key Points:The Success of Insects

Evidence of Success

  • Numbers
  • Longevity
  • Diversity
  • Reasons for Success
    • Physical size
    • Flight
    • Fecundity
slide3
Insects by most measures,

are the single MOST successful animal group

in the entire evolutionary history of the earth!!

evidence of insect success the numbers
Evidence of Insect SuccessThe numbers

Number of species:

  • 1,000,000 named
  • 5/6thof all known animal species

Number of living [extant] individuals:

  • 1018 {one million billion}
  • 1015 ants!!!

Biomass:

birds = 1 lb per acre

humans = 14 lbs per acre

insects = one ton per acre {tropics}

FYI

evidence of insect success longevity as a taxon
Evidence of Insect SuccessLongevity as a taxon

Insects first appeared 400 million years ago

(before dinosaurs!)

Mammals: 200 mya

Primates: 70 mya

Genus Homo: 2 mya

H. sapiens sapiens: 40,000 years ago

FYI

slide7

Evidence of Insect SuccessEcologicalDiversity

Insects are everywhere!

    • Terrestrial, fresh water & marine
    • Only polar ice caps without insects

Latitude

  • butterflies at 80° North (within the Arctic Circle)
  • mosquitoes at 70° North
  • midges at 65° South (Antarctica)

Altitude

  • Hemiptera @ 16,500 feet
  • Orthoptera @ 16,000 feet
  • Lepidoptera @ 15,000 feet
  • Hymenoptera @ 12,000 feet

FYI

FYI

FYI

slide8

Evidence of Insect SuccessEcologicalDiversity

Temperature

Majority of insects arestenothermic& ectothermic(not always)

Cold

- Stoneflies & mosquito larvae active @ 0° C

- Midge larvae recovered from immersion in liquid nitrogen (-190° C)

Heat

- Hot springs at Yellowstone with midge larvae active at 49°-51° C

slide9

Reasons for Insect Success

Physical Size

Insects are small (relative to humans)

Average Insect = the housefly

  • (Muscadomestica)
  • 5-7mm
slide10

Reasons for Insect Success

Physical Size

Insects are small (relative to humans)

  • Extremes:
    • Smallest= 1/5th of a mm (1/100th of an inch)

FYI

Fairyfly next to a paramecium and an amoeba

Family: Mymaridae, Fairyfly

(a tiny wasp!) next to a match stick.

slide11

Reasons for Insect Success

Physical Size

Extremes:

Largest = 6 in. Largest Wingspan = 12 in.

Rhinoceros beetle Dynasteshercules

  • Brazilian moth Thysaniaagrippina
slide12

Meganeura

  • Extinctdragonfly (300 mya)
  • with a wingspan of 24 inches!
slide13

Reasons for Insect Success

Physical Size

Extremes:

Longest = 22 in. Heaviest= 100 g or ¼ lb.

(weight of small bird!)

Chan’s MegastickPhobaeticuschani

  • Goliath Beetle FornasiniusFornasini
slide14

Reasons for Insect Success

Advantages of being small

1) Less food to reach maturity

  • honey bee: egg to adult in 21 days on 300 mg of food (1/80th of an ounce)

2) Utilize small retreats to escape/avoid predators

3) Able to utilize a “small” food resource

  • an egg of another insect, for example!!
slide16

Reasons for Insect Success

Flight

Most, but not all insects are capable of flight

APTEROUS (without flight)

- Primitive groups that never had wings

- Collembola - Silverfish

PTERYGOTA = winged (most living insects)

- Some Pterygota secondarily lost their wings

i.e., Fleas

slide17

Reasons for Insect Success

Flight

Insects were the firstanimals to fly

  • as long ago as 330 mya
  • 100 million years before birds & mammals

ADVANTAGES of Flight

1) Food Capture

2) Escape from Predators

3) Dispersal to new environments

4)SEX

slide18

Reasons for Insect Success

Physics of Flight

Wing Beat

- butterflies 8-12 b/s

  • locust & grasshoppers 18-20 b/s
  • dragonflies 20-30 b/s

[humming birds 30-50 b/s]

  • honey bee 190 b/s
  • mosquitoes 600 b/s
  • a midge >1000 b/s

Speed of Flight

  • honey bee = 15 mph (22 ft/sec)
  • dragonfly = 35 to 40 mph
slide19

Reasons for Insect Success

Fecundity

FECUNDITY = fertility = fruitfulness = “r” = intrinsic rate of increase

Paradigm of the house fly [Dr. Hodge]

one female & one male in April

Assume that all progeny live

= 1.91 x 1020 flies by August!!!

= enough flies to cover the earth with a layer of flies 47 feet thick!!!!

…Wrong says Dr. Oldroy,

only an area the size of Germany

slide20

Reasons for Insect Success

Fecundity

Dr. Herrick & his cabbage aphids:

    • 12 generations between March 31 & August 15 =
    • 822 million tons!!!
  • predators & parasites
  • finite food supply
  • weather
  • …Cute, but ridiculous
  • as these examples leave out:
slide21

Reasons for Insect Success

Fecundity

  • The average “r” value for an insect is 100to150fertilized eggs in her life time.
  • Not so bad relative to humans, with the average female producing 400 eggs of which 2.2 will be fertilized.
slide22

Reasons for Insect Success

Fecundity

High Fecundity

+ a short life span

+ a short generation time =

A group of organisms more responsive to short-term environmental change (selective pressures) =

A group with pronounced evolutionary success!!

key points the success of insects1
Key Points:The Success of Insects

Evidence of Success

  • Numbers
  • Longevity
  • Diversity
  • Reasons for Success
    • Physical size
    • Flight
    • Fecundity
glossary

Back to lecture

Glossary

Extant – adj. Still in existence; surviving.

Taxon - noun, plural: taxa (taxonomy)

(1) Any group or rank in a biological classification into which related organisms are classified.

(2) A taxonomic unit in the biological system of classification of organisms, for example: a phylum, order, family, genus, or species.

Stenothermic - adj. Capable of living or growing only within a limited range of temperature.

Ectothermic - adj. Of or relating to an organism that regulates its body temperature by exchanging heat with its surroundings; cold-blooded.