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Flowers and Reproduction (Flower Structure and Cross-pollination image,…
Sexual Reproduction 
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Gametophytes
Microgametophyte
30% of angosperm species formation of sperm cells occurs even while pollen is still located withing the anther :black_flag:
after pollen grain lands on a stigma, it germinates by producing a pollen tube that penetrates into the loose, open tissues of the stigma :check:
microspore nucleus migrates to the side of the pollen grain and lies next to the wall and divides mitotically
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microspores develop into microgametophytes, each microgametophyte is very small and simple :star:
Megagametophyte
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within the ovule, surviving megaspore develops into a megagametophyte :check:
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Fruit Development
the entire fruit wall, whether composed of 1,2, or all 3 layers is the pericarp :star:
3 layers become distinct
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exocarp is the outer layer, the skin or peel
as the ovule develops into a seed, the ovary matures into a fruit. Development varies with the nature of the carpels as well as nature of the fruit :check:
Flower structure
petals
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are leaf like as they are broad but contain pigments other than chlorophyll, have fewer to no fibers and tend to be thinner :check:
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attract correct pollinators due to shape, color, and orientation
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stamens
Microspore mother cells or microsprocytes continue to enlarge then undergo meiosis each producing 4 microspores. :<3:
neighboring anther cells, in a layer called the tapetum act as nurse cells, contributing to microspore development
have two parts
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anther is composed of diploid cells and in each anther, 4 long columns of tissue become distinct as cells enlarge and undergo meiosis :recycle:
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located above the petals and collectively known as the androecium, incorrectly referred to as male part, produces pollen :check:
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sepals
are modified leaves that enclose other flower parts when they mature, are typically thickest, toughest of the flower parts
protect flower bud as they develop and maintain high humidity and protect plant from nectar robbing insects and birds :star:
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Carpels
inside every ovary are placentae, regions of tissue that bear small structures calles ovules :star:
ovules have short stalk, called funicules and have a central mass of parenchyma called nucellus :check:
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megaspores differ from microspores because ovules and carpel do not dehisce and the megaspore remains enclosed :red_flag:
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ovules develops into a seed after its egg is fertilized and surrounding ovary develops into a fruit :green_apple:
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Fertilization
in angiosperms only, second sperm nucleus released from the pollen tube migrates from the synergid into the central cell :star:
both sperm nuclei undergo fusions, one with the egg nucleus and the other with the polar nuclei called double fertilization :star:
undergoes karyogamy with both polar nuclei establishing a large endosperm nucleus that is triploid :red_flag:
Endosperm nucleus initiates a dynamic cytoplasm and the central cell enlarges enormously, usually without cell division :check:
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because sperm sheds its protoplasm as its passes through the synergid, its contributes only its nucleus during karyogamy :star:
mitochondria and plastid genes of the embryo are inherited only from the ovule parent, except in conifers :check:
sperm does not carry mitochondria or plastids into the egg, organellar genes from pollen parent are rarely inherited by zygote
syngamy of sperm and egg involves both plasmogamy, fusion of the protoplasts of the gametes and karyogamy fusion of nuclei :check:
it penetrates nucellus and reaches egg apparatus, entering one synergid. pollen tube tip bursts and releases both sperm cells
sperm nucleus enters the egg, then is drawn to and fuses with the egg nucleus establishing a diploid zygote nucleus
as pollen tube grows downward through the style toward the ovule, its guided to the micropyle
The plant life cycle
a life cycle with two generations, sporophyte and gametophyte is said to be an alternation of generations. :star:
because gametophytes do not resemble sporophytes at all this is an alternation of heteromorphic generations :check:
plant spores are the opposite they cannot undergo syngamy but each undergoes mitosis and grows into new haploid plant called gametophyte :star:
in all vascular plants, a haploid gametophyte does not even remotely resemble a diploid sporophyte.
is a tiny mass of cells with no roots, stems, leaves, or vascular tissue :check:
during sexual reproduction, sporophyte is reduced but does not produce new diploid plant like itself but rather a haploid plant :check:
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life cycles are complex in plants, the trees, shrubs, and herbs are just one phase called the sporophyte phase or sporophyte generation :check:
difference between gametes and spores is great, gametes can fuse with other gametes in a process called syngamy or fertilization :star:
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Diploid adults have sex organs that produce haploid sex cells called gametes either sperms or eggs by meiosis :star:
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fertilized egg is called a zygote, and will grow into a new individual :check:
Flower Structure and Cross-pollination
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Animal- Pollinated Flowers
mutations in plants increased due to the random insertion of pollen by insects that did not recognize specific plants
this began to create specific mutations such as size, shape, color, nectar production etc.
many lines of insects and flowers underwent coevolution, flower becoming adapted for visitation by a specific insect :star:
most flowers are radially symmetrical meaning they produce mirror images when cut longitudinal. these are called actinomorphic or regular :sunflower:
insect-flower association began around 120 million years ago, neither insects or flowers were sophisticated :black_flag:
in many species, flowers and pollinators have coevolved in such a way that the flowers are now also bilaterally symmetrical called zygomorphic :check:
most animals and plants relationships are a battle, animals try to eat or lay eggs in plants and plants use chemicals to defend :warning:
mutations have helped plants defend themselves and also indicate to friendly animals to come and pollinate
cross pollination
with cross pollination, sperm cells and egg cells fro different plants unite, resulting in new combinations of genes :star:
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self pollination is pollination of a carpel by pollen form the same flower or another flower on the same plant :<3:
if plant is isolated by distance or lack of pollinators, self pollination allows it to set seed and propagate its genes rather than lose them :check:
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Ovary position
all flower organ primordia are initieated at the receptacle apex, primordia crowd together, stamens, petals, sepals fuse . :star:
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most common arrangement is which there is no fusion to the ovary occurs and ovary is above other flower parts is :warning:
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intermediate, partially buried ovaries are half-inferior with perigynous flower parts :check:
adaptations include long styles and stamen filaments, burying ovaries deep within flower provided further protection :check:
Ovary and ovules must be well protected from pollinators, flower must bring animal close in order to effect pollination :lock:
Wind pollinated Flowers
sepals are usually reduced or absent, ovaries need no special protection, zygomorphy is not advantageous :!:
wind pollinated individuals produce up to several thousand small flowers, creates huge surface area for the plant :checkered_flag:
wind pollinated plants have a distinct set of modifications is adaptive, attracting pollinators is unnecessary
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Fruit Types and Seed Dispersal
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Classification of fruit types
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simplest fruits are grasses, are caryopses
one method of classifying fruits is whether the fruit is dry or fleshy. dry fruit is not typically eaten during seed distribution, fleshy is opposite :check:
beans and peas form from a single carpel that contains several seeds, but do not fuse seeds :red_flag:
fruits and seeds carried by wind must be lights and often have wings or parachutes. usually dry :star:
Animals carry fruit in a variety of ways, they can stick to fur, be eaten and digested, and crushed and opened by stepped on :check:
grapes and tomatoes are examples of simple flesh fruits, coat provide some protection but have slippery seed coats :green_cross:
pomes differ as they develop form inferior ovaries and inner tissue is true fruit and outer is accessory, seeds protected by bitter inner core :pear:
seeds are not distributed at random but are moved though the environment to specific sites when eaten by animals
when seed is digested, may find itself in a pile of fertilizer and are well adapted to the new microenvironment :<3:
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Inflorescences and Pollination
production of the pedicel, recepticle, sepals, and petals can be thought of as packaging and advertising cost, large flowers have advantage :check:
small flowers with only a few ovules can group together and create an inflorescence, to give a collective visual :star:
reproductive success is measured in terms of the number of healthy, viable seedling that become established. :!:
flower size can also effect amount of nectar stolen, flowers pollinated, predators etc.
positioning of flowers on an individual plant is important few species are only able to produce limited amount of flowers :!:
when smaller flowers are grouped into inflorescences, two types of arrangements occur
determinate inflorescences which has a limited potential for growth. terminal flowers typically open first stunting growth :check:
indeterminate inflorescences, lowermost or outermost flowers open first not limiting the growth potential
many species do not have a main axis, and elongated pedicels
Asexual Reproduction
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fragmentation is when a large spreading or vining plant grows to several meters in length and individual parts become self-sufficient by establishing adventitious roots :black_flag:
modifications like the cacti in which branches are poorly attached and when broken, form roots and become independent :check:
if middle portion dies, ends become separated and act as individuals
concepts
with asexual reproduction, progeny are never more fit than the parent, but during sexual reproduction :star:
sex cells of one plant combine with those of one or several others resulting in many new gene combinations :red_flag:
sex cells are so small that many can be produced by a single plant and many new combinations can be tested inexpensively :black_flag:
pollen from one plant can be blown or carried by pollinators to the flowers of hundreds of other plants and vice versa for receiving :checkered_flag:
during seed/fruit maturation, those embryos with severely mismatched genes abort and use no further resources
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if an environment is relatively stable during several life times it is advantageous to reproduce asexually :check:
if environment is not stable, offspring can find themselves in conditions that they are poorly adapted to.
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