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Flashcards in lecture 10 Deck (18):


-mosses are gametophyte dominant
-the cushiony green growth that we associate with moss is the gametophyte


five stages of the moss life cycle

1. gametes develop in male and female gametangia
-these are usually located on seperate plants
-flagellated sperm swim through a water film to reach the egg in the female gametangium
2. after fertilization the zygote remains in the gametangium
3. in the gametangium the zygote divides by mitosis
-develops into a sporophyte embryo and then a mature sporophyte
-sporophyte remains attached to the gametophtye
4. meiosis occurs in the aporangia, at the tips of the sporophyte stalks
-following meiosis, the haploid spores are released from the sporangium
5. spores undergo mitosis and develop into gametophyte plants



these plants are sporophyte dominant
1. gametophyte is very small
-often have a distinct heart- like shape
-flagellated sperm requiring mositure to reach the egg
2. zygote remians on the gametophyte
3. the zygote develops into an independant sporophyte
4. within the clusters or sporangia cells undergo meiosis producing haploid spores which are then released
5. spores develop into gametophytes by mitosis


all seed plants have a special structure within the sporophyte where all stages of reproduction occur



in gynosperms the specialized structure where reproduction occurs is called

-each scale of the cone contains sporangia which produce spores by meiosis
-these spores are not released but give rise to gametophytes within the cone structure
-the gametophyte go on to produce gametes which then unite and form a new sporophyte


pine trees have two types of cones which produce spores

-smaller cones called pollen cones and produce male gametophytes
-these contain many sporangia which produce many haploid spores by meiosis
-male pollen grains (gametophytes) develop from these spores
-mature pollen cones release millions of micoscopic pollen grains in clouds
-these pollen grains care carried by wind
-they contain cells that will develop into sperm if they land on a cone containing a female gametophyte



-the ovulate cone, producing the female gametophyte is larger than a pollen cone
-each of the cones stiff scales contains a pair of ovules
-each ovule contains a sporangium covered by a protective called the integument


pollination occurs in gymnosperms when

a pollen grain lands on an ovulate scale and eneters an avule
-following pollinantion the scales grow together, sealing the cone until the seeds mature
-now meiosis occurs in a spore mother cell within the ovule


development of gymnosperms

-over the course of months one surviving haploid spore will develop into the female gametophyte
-this gametophyte will produce eggs
-a tiny tube grows out of the pollen grain
-this tube digests its way through the ovule
-eventually sperm is released near an egg
-fertilization usually occurs more than a year after pollination
-all eggs in an ovule are usually fertilized
-only one of these zygotes will fully develop into a sporophyte embryo
-the ovule will mature into a seed
-the seed contains the embryo's food supply and tough seed coat
-the food supply is the remains of the female gametophyte
-the seed coat is the ovules integument
-typically seeds are shed two years after pollination
-the seed is dispersed by wind
-under favorable conditions the seed will germinate and its embryo will develop into a pine seeding


differences and similarities between angiosperms: flowering plants and gymnosperms

-flowers are the site of pollination and ferilization
-much like pine cones:
-flowers house sperate male and female sporangia and gametophytes
-mechansims of sexual reproduction (pollination and fertilization) are similar also
-differ from pine cones:
-each structure of the flower is highly specialized for very different functions


angiosperms: structure

-floral structures are attached in a circle to a receptacle at the base of the flower
-the outer layer of the circle contains seapals which are usually green
-these enclose the flower before it opens
-the next layer, after the sepals are removed are the petals
-these are very noticeable and attract pollinators
-these showy petals are key to the success of angiosperms
-removal of the flower petals reveals the stamen filaments
-at the top of each of these filaments is the anther
-the anther is a sac containing the male sporangia
-this will eventually release pollen
-the carpel is the structure located at the center of the flower
-this is the female reproductive structure, including the ovary
-this is the unique angiosperm adaptation which encloses the ovules
-each ovule contains sporangium that will produce a female gametophyte and eventually become a seed
-the ovary will mature into a fruit which aids in seed dispersal


angiosperms: fertilization

-this group of plants is sporophyte dominant
-the gametophyte generation is produced within its body
-meiosis occurs within the anther of the flower
-this produces haploid spores which undergo mitosis
-these will form the make gametophyte (pollen grains)
-meiosis in the ovule produces a haploid spore that under goes mitosis
-this forms the few cells of the female gametophyte
-one of these cells is destined to become an egg
-pollination occurs when a pollen grain lands on the stigma
-the pollen grain is carried by wither wind or an animal
-a tube grows from the pollen grain to the ovule and a sperm fertilizes the egg (same as in the gymnosperms)
-this forms a zygote


angiosperms: reproduction

-a seed develops from each ovule
-each seed consists of an embryo surrounded by a seed coat and a food supply
-the embryo is a new sporophyte
-as the seed develops the ovaries wall thickens
-this forms the fruit that encloses the seeds
-when conditions are favorable the seed germinates
-as the embryo grows it uses the food supply from the seed until it can begin photosynthesis
-eventually it develops into a mature sporophtye completing the life cycle
-flowers attract animals which carry pollen more reliably than wind
-a key adaptation of angiosperms
-they are also able to produce very rapidly
-fertilization occurs in just 12 hours after pollination


fruit structure

-fruits are the ripened ovary of the flower
-aids is seed dispersal
-some angiosperms rely on the wind for seed dispersal
-many angiosperms produce fleshy, ediable fruits which attract animals-food source
-during development the fruits remain green and thus camoflaged against their backdrop
-when ripe fruits become brightly colored advertising their presence to animals such as birds and mammals
-when the fruit is eaten most of the seeds which are tough pass unharmed through the digestive tract of the animal
-the animal may then deposit the seeds, along with fertilizer some distance away from where it initially found the fruit


animal pollination and angiosperm evolution

-not all flowers have colorful accessories and sweet scents
-red maple has many anthers but not petals
-relies on wind for pollination: not fool proof
-massive amounts of pollen must be produced to ensure that some makes it to another plant and fertilization takes place
-the columbine has an elaborate flower: vibrantly colored
-this is associated with high energy cost
-this investment pays off when a pollinator carries the plant's pollen to another flower
-the pollinator is attracted to the vibrant color
-estimated that 90% of anigosperms use animals for pollination
-animals visit the flowers in search of a meal
-flowers provide meal in form of nectar which is a high energy fluid
-the colorful petals and strong fragrance mark the plant as a food source


two major types of angiosperms

monocots and eudicots
-this classification is according to the first leaves that appear on the plant embryo
-these embryonic leaves are called seed leaves or cotyledons
-monocots have one coltyeden
-eudicots have two cotyledons



-large number of related plants including lilies and orchids
-have a number of distinctive characteristics
-leaves with parallel veins
-stems contain vascular tissues arranged in scattered bundles
-flowers contain petals and other parts in multiples of three
-roots form a shallow, fibrous system spreading out below the soil surface
-this arrangement permits a huge surface area which reduces erosion



-most angiosperms are eudicots
-includes most shrubs and trees, crops, fruits, and vegetables
-characteristics arrangements includes:
-multi-branched network of veins
-vascular bundles arranged in a ring
-petals and other parts are found in arrangements of four or five
-root is large and vertical-taproot
-goes deep into soil