BIOL 108 Lab 3

alternation of generations

species alternates between two distinct phases - one haploid and one diploid - defined by the events of meiosis and fertilization. In land plants, meiosis results in the production of haploid spores

spores

single cells that germinate and develop into multicellular plants that produce the sex cells or gametes. These plants, called gametophytes, not only bear the male and female gametes, but also serve as the site for fertilization. The sperm and egg join to form a zygote, which initiates the diploid phase of the life cycle, the sporophyte

sporophyte

the visibly dominant generation in ferns and seed plants, while the gametophyte is very small and not easily seen. The small gametophyte in ferns develops and matures independently from the sporophyte, in the soil below, whereas the gametophyte of seed plants develops within special structures in the sporophyte.

Ceratopteris richardii

a homosporous fern that has two distinct phases to its life cycle, a simple haploid gametophyte, and a more complex, diploid sporophyte. There are two different types of gametophytes that developed from the spores - hermaphroditic gametophytes, which have both archegonia and antheridia, and male gametophytes which have only antheridia. The archegonia produce eggs and the antheridia produce sperm. In the presence of water, flagellated sperm are released from the antheridia, start to swim and seek a receptive egg. Simultaneously, water also causes the neck on the archegonium to open and release a chemical that causes the sperm to swarm at the neck opening. The sperm swim down the neck and fertilize the egg. The resulting diploid zygote undergoes mitotic cell division to form the embryo, which in turn develops into a new diploid sporophyte

dermal tissue

outer layer of cells composed of the epidermis and the cuticle; sometimes show hair and trichomes

ground tissue

fills the space between the epidermis and vascular bundles; has specialized cells for photosynthesis, support, and storage

cortex

contains cells for storage and support; may have chloroplasts to participate in photosynthesis

vascular tissue

also provides support for vertical growth; beneficial to overcome the challenge of the absence of bouyancy for plants when they colonized land

pith

has storage cells

convergent evolution

an independent evolution of similar adaptations. We see it in many specialized groups of plants - note that these similarities are analogous (similarity in structures not derived from a common ancestor) as opposed to homologous (similarities shared by groups as well as their common ancestor). These loose groupings of plants found similar solutions to the same problem

epiphytes

adapted to moist and humid environments - heavy precipitation like tropical and subtropical rainforests; have important competition for light; they grow on the surface of other plants and are not connected to the soil; not parasitic; attached to the host trunk or higher in the canopy; get water and nutrients from the air, rain, or debris - EG. MOSSES, BROMELIADS, ORCHIDS; have better access to light higher in canopy, pollinators, seed dispersal but rely on air moisture/run off and have limited nutrients access

Insectivory

Habitat: acidic bogs, fens, rainforest; are common in habitats with low nutrients (consume insects or arthropods) and trapping mechanism evolved independently many times); EG. SNAP TRAP, PITFALL TRAP, LOBSTER POT TRAP, ADHESIVE; limited photosynthetic activity and easily affected by competition and environmental disturbances

desert adaptations

Habitat: extreme temps, aridity, sandy or gravelly soil, limited access to organic matter; water storage in leaves, stems, roots; large and shallow roots, cuticle, no leaves - more spines, thorns, prickles; EG. CACTI, ALOE, BRITTLEBUSH, AFRICAN MILK TREE; require protection and have a growth delay

tropical adaptations

habitat: warm climate, high humidity, abundant precipitation, fertile soil and dense vegetation; have large leaves and leaf drips to prevent fungal growth; extra support with buttress roots or arial roots; prone to damage from precipitation and fungal organisms; high competition

scientific method

the series of steps we use to answer an experimental question. It all starts with an observation, and then an experimental question based on that observation and background research. Then you propose an answer to that question (hypothesis), design an experiment to test your hypothesis, and then predict the outcome of your experiment if your hypothesis is true. Once you perform your experiment and analyze your results, you draw conclusions and compare those to your hypothesis. Regardless of whether your results support with your hypothesis, it is still a result worth communicating!