pollen and spore examination

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Pollen and Spore Examination. Introduction. Pollen and spore information can be used to determine the following: Was the body moved? Where did the crime take place? What season did the crime take place? Did the crime take place in the day or night? - PowerPoint PPT Presentation


Pollen and Spore Examination

Pollen and Spore ExaminationIntroductionPollen and spore information can be used to determine the following:Was the body moved?Where did the crime take place?What season did the crime take place?Did the crime take place in the day or night?Forensic Palynology study of pollen and spore evidence to help solve a crime.Pollen reproductive structure that contains sperm from seed plantsSpore reproductive structure that develops into an adult in algae, some plants, and fungi.

Pollen ProducersPollen fingerprint number and type of pollen grains found in an area at a particular time of year.Plant kingdom is divided into two groups based on how they reproduce: seeds or no seeds.Seeds: Gymnosperms (evergreens) and Angiosperms (flowering plants)Nonseeds: Ferns, moss, liverworts, horsetails, club mossesGymnospermsMeans naked seed the seed is not protected like they are in flowering plantsMost numerous group of gymnosperms are the conifers (evergreens)Produce their seeds within a cone. Heres how:Pollination occurs when pollen lands on a female cone, grows and releases the sperm near the egg.Once the egg is fertilized, a seed develops (containing an embryo)

AngiospermsFlowering plantsProduce seeds within an enclosed fruitParts of a flower:Types of PollinationImportant in forensics in determining the presence or absence of pollen in a place or on an object of a crime sceneSelf pollination vs. Cross pollinationSelf pollen transfer from anther to stigma within the same flower.Cross pollen transfer involving two distinct plantsSelf pollinating plants has lower value because they produce less pollenMethods of pollinationWind pollination produce a lot of pollen (good and bad)Good well represented in the pollen profile of a crime sceneBad less effective in determining direct linksFlowers are usually nonfragrant, lack color, small

Animal pollination insects, birds, bats, monkeysFlowers are fragrant and showy Pollen grains are durable and can adhere to thingsStrong evidence of contactProduce less pollen

Dandelion wind pollinatedBurs animal pollinated (poor dog)

Notice the hooks on the ends of the spikes

Maple tree seeds helicoptersMethods of pollination continuedWater pollination Rarely preserved because it is composed of only a single layer cell wall made of cellulosePollen will decompose if removed from waterLimited use, excepts for drowned victimscontents of the lung can be emptied and analyzed.

Spore ProducersAlgae Adapted for dispersal in water or airFerns and MossesRelease spores into the airBecause of this, forensics is most interested in theseFungiProduce a large amountMold, yeast, mushroomsCan be found practically everywhereBacteria (an exception)Some bacteria produce thick-walled, resistant spores called endospores.Different in structure and arent used in reproductionBacteria that causes anthrax and botulism are examples

Spore DispersalWindWaterSpore ejectionAnimal disperal (they eat the spore and deposit it somewhere else in their feces)

Spore analysis has one advantage over pollenit is possible to grow the organism and identify the species exactly.Pollen and spore identification in solving crimesExine -- The hard outer layer of a pollen or spore grain Has a unique and complex structure under the microscope. Larger pollen grains cant travel far (can only drift with the wind mile) (corn)Wind-dispersed pollen grains are simple, have thin walls, easily preservedAnimal-dispersed pollen grains are large, sticky, highly ornamented, thick-walled and easily preserved

Pollen and spore identification in solving crimes ContinuedIdentification of pollen and spore grains is species specificHelp determine seasonHelp determine locationIf not native to the crime scene, body was moved.Pollen and spores are difficult to eliminate by the suspect because they are microscopicThey are resistant to dehydration and decomposition (can be found in sediment from millions of years ago)Locards principle is easily applied (especially animal dispersed seeds)


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