Forensics Outline Chapter 8

INTRODUCTION
1)Several specialized forensic fields are devoted to studying biological evidence at a crime scene. One of these fields is forensic palynology, the study of pollen and spore evidence to help solve criminal cases 2)A spore is another kind of reproductive structure that can develop into an adult that is found in certain protists (algae), plants, and fungi
3)The use of both pollen and spores in forensic studies is based on Locard’s principle of exchange

POLLEN PRODUCERS
1)Knowledge of pollen (and spore) production is an important factor in the study of forensic palynology
2)By understanding pollen production patterns for plants in a given location, one can better predict the type of pollen “fingerprint” to expect in samples that come from that area. A)Pollen’s “fingerprint” is the number and type of pollen grains found in a geo- graphic area at a particular time of year.

GYMNOSPERMS
1)The seeds of gymnosperms, the oldest seed plants, are exposed to the outside and are not enclosed in a protective chamber like the angiosperms. A)Conifers are the largest group of gymnosperms . They include pines, spruces, firs, junipers, and other evergreen plants that usually retain their leaves or needles all year.
Many conifers produce their seeds within a hard, scaly structure, called a cone. B)Female cones, which are typically larger than male cones, contain eggs inside structures called ovules. C)The males cones of conifers occur in clusters and release large amounts of pollen grains to be spread by wind currents.
2)Pollination occurs when pollen is trans- ferred from the male cone to the female cone. The pollen grain germinates, releasing sperm that will fertilize the egg found in the female cone.

ANGIOSPERMS
1)Angiosperms, the most recent plant group to evolve, are known as the flow- ering plants, and they produce seeds within an enclosed fruit A)Angiosperm success and diversity are based on several factors, such as the protective nature of the fruits that also help disperse the seeds. Because angiosperm plants are found in so many places
2)The basic reproductive unit of an angiosperm is the flower. The pistil is the female part of a flower that produces eggs. A)The three main parts of the pistil are the stigma, style, and ovary. The stigma is the area where pollen lands. B)A pollen tube produced by a germinat- ing pollen grain can grow down the long, thin style until it reaches the ovary. There may be one or hundreds of egg-containing ovules surrounded by the ovary, but the num- ber is species-specific.

TYPES OF POLLINATION
1)Pollen (and spore) dispersion patterns are important to con- sider in forensic studies for analyzing palynological samples that come from the crime-scene area. The pollination strategy of the plant is an important factor in determining the presence or absence of pollen in a place or on an object of a crime scene.
2)Before a sperm can fuse with an egg during fertilization, pollination must occur in all seed plants. Pollination is the transfer of pollen from the male part of a plant to the female part of a seed plant.

METHODS OF POLLINATION
1)A significant number of flowering plants are also wind-pollinated, but many are pollinated by specific animals, such as insects, birds, bats, and even monkeys. A)These plants have fragrant or showy flowers to attract the animals B)Water-pollination is another type of pollination. Pollen from aquatic angio- sperms, such as sea grasses, is dispersed by water. C)Aquatic plant pollen that is released under the water is composed of only a single-layered cellulose wall. Thus, this kind of pollen is rarely preserved in sediments and generally decomposes if removed from water.

SPORE PRODUCERS 1)Spore production is also important. Knowledge of spore production and the different organisms that produce spores can help in making predictions about the expected spore profile (fingerprint) in an area. The spore producers include certain protists (algae), plants, and fungi. Some bacteria also produce a unique type of spore
2)Algae, the ancestors of plants, produce reproductive spores that are adapted for dispersion in water or air. Some land plants produce spores from a structure known as a sporangium, gills A) Seedless plants, such as ferns and mosses, release the spores into the air. Thus, seedless plants are the spore-producing plants of interest in forensic studies. Dispersed spores can develop into new individuals under favorable conditions. B)Fungi, such as mold, baker’s yeast, and mushrooms, produce large numbers of spores. Fungi can produce spores in two ways: asexually and sexually. During asexual reproduction, spores are made by a single fungus, and these spores produce new fungi identical to the original fungus. D)Fungal structures called spo- rangia release spores, and these spores can grow into new fungi under good environmental conditions

BACTERIA: AN EXCEPTIONAL CASE
1)When environmental conditions are harsh, some bacteria form thick-walled, resistant spores, called endospores. Bacterial spores are different from the other class of spores produced by fungi, algae, and plants because endospores, unlike other spores, are not used in reproduction, and bacteria can produce only one at a time.

SUMMARY
1)Forensic palynology can provide information about the geographic ori- gin of a crime and the time or season when it took place.
2)Pollen is a reproductive structure containing male gametes in seed plants. Spores are reproductive cells produced by some protists, plants, and fungi.
3)Nonseed plants such as ferns reproduce with spores.
4)Seed plants include gymnosperms (plants that do not produce fruits) and angiosperms (plants that do produce fruits). A)Both gymnosperms and angiosperms produce pollen.
5)Plants may disperse pollen on the wind, in the water, or by the move- ments of animals.
Pollen from wind-pollinated plants is more common in forensic samples, but pollen from insect-pollinated plants tends to provide more specific information about location.
Pollen evidence must be collected at a crime scene and include baseline samples from the area for comparison.
Collection of pollen and spore evidence must be performed carefully to avoid contamination.
Pollen is examined microscopically and compared with reference collec- tions to identify, if possible, the exact species that produced it.