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Ch 10: Flowers and Reproduction - Coggle Diagram
Ch 10: Flowers and Reproduction
Concepts
Reproduction can serve two different functions. Producing offspring that have identical copies of the parental genes or generating individuals that are genetically different from their parents.
If the environment is stable during several lifetimes, it is selectively advantageous for an organism to reproduce asexually by budding or sending out runners.
In asexual reproduction the offspring are never more fit than the parent- take the parent genes.
If some of the plants in an area are different genetically they have a better chance of surviving overall
Fragmentation
- A large spreading or Vining plant grows to several meters in length, and individual parts become self-sufficient by establishing adventitious roots
If all of the plants in An area are genetically identical, Something such as a rare freeze could wipe all of them out.
Sex cells are so small that many can be produced by a single plant. This allows for experimentation of different genes for "cheap"
Sexual reproduction allows for a Genetically diverse species.
Two individuals are required in sex cells must move from one Plant to another. In seed plants, pollen can be carried by wind, insects, and birds. The pollen can be lost or eaten before it makes its way to another plant or tree
Seeds
- Produced by sexual reproduction, often have a means of long-distance dispersal. This can cause the seeds to become widely scattered and germinate in many diverse sites. In these new sites, it could face new microclimates, soil conditions, and new predators and pathogens.
If endosperm is abundant the seed is
albuminous
If endosperm is sparse or absent at maturity the seat is
exalbuminous
The Plant Life Cycle
Sporophytes
are always diploid and have organs with cells capable of undergoing meiosis which results in haploid
spores
. Gametes can fuse with other gametes in a process called
syngamy
or
fertilization
Alternation of generations
- life cycle with two generations- sporophyte and gametophyte. This is an alternation of
heteromorphic generations
since they do not resemble each other.
during sexual reproduction sex cells of one plant combined with those of one or several others resulting in new gene combinations
Flower Structure
Stalk-
Pedicel
Receptacle
where the other flower parts attach
Sepals
- The lowest and outer most of the four floral appendages. They are modified leaves that surround and enclose the other flower parts as they mature. Also the thickest, toughest, and waxiest of the flower parts. Protects the flowering bud. Also referred to as calyx
Petals
- Make up the corolla. Sepals and petals both make up the perianth.
Stamens
- together known as the androecium. Commonly referred to as the male part of the flower. 2 parts- filament and anther (where pollen is produced.)
Anther is composed Of diploid cells and in each anther For long columns of tissue become distant as some cells enlarge and prepare for meiosis. These
microspore mother cells or microsporocytes
Continue to enlarge and then undergo meiosis.
tapetum
- Neighbors anther Cells and acts as a nurse, contributing to microspore development and maturation
carpels
- constitute the gynoecium, Located at the highest level of the receptacle. Three main parts including a stigma that catches pollen grains, a style that elevates the stigma to a useful position, and an ovary where megaspores are produced.
Inside the ovary are
placentae
, Regions of tissue that bear small structures called ovules.
There are four types of flower appendages: sepals, petals, stamens, and carpels. Complete flowers have all 4.
In the torpedo stage, the embryo is an elongate cylinder: A short axis is established, consisting of
radicle, epicotyl, and hypocotyl
.
The integuments That surround the nucleus expand and mature into the
seed coat (testa)
fruit
As the ovule develops into a seed, the ovary matures into a fruit. The
exocarp
is the outer layer, the middle is the
mesocarp
, and the inner most is the
Endocarp
. The entire fruit wall is called the
pericarp
Gametophytes
Embryo sac
- Technical term for a multi. nucleate megagametophyte
Plasmogamy- the protoplasm of two parent cells (usually from the mycelia) fuses together without the fusion of nuclei, effectively bringing two haploid nuclei close together in the same cell.
In angiosperms only the second sperm nucleus released from the pollen tube my grades into the central. It undergoes karyogamy With both polar nuclei, establishing a large
endosperm nucleus
suspensor
is delicate and ephemeral in angiosperms. The end of the embryo farther from the suspensor initiates 2 primordia that grow into
cotyledons
Flower structure and cross pollination
cross-pollination
- Pollination of a carpel by pollen from a different individual
Self-pollination
- Pollination of a carpel by pollen from the same flower or another flower on the same plant
Compatibility barriers
- Inhibits Self pollination in many species, especially mini important crop species. Inhibited by chemical reactions between pollen and carpels that prevent pollen growth
If a flower lacks stamens or carpels, Sexual reproduction is dramatically affected. The flower would be incomplete and imperfect. If a flower has both it is a perfect flower.
Dioecious life cycle- microgametophytes, megagametophytes, staminate sporophytes, and carpellate sporophytes.
Animal pollinated flowers
flowers underwent coevolution due to insects choosing the most nutritious flowers to visit and distributing pollen among them from other flowers
Most flowers are Radially symmetrical and called
actinomorphic
or regular
In many species flowers and pollinators have coevolved in such a way that the flowers are now also bilaterally symmetrical-
zygomorphic
Inflorescences and pollination
If many flowers are grouped together it is called an inflorescence. They gave a collective visual signal to pollinators; one small flower may be overlooked, but not 100 close together
Determinant inflorescences
- Has only a limited potential for growth because the inflorescences Apex is converted to a flower, ending its possibilities for continued growth.
Indeterminant inflorescence
- The lowest or outer most flowers open first, and even while these flowers are open, new flowers are still being initiated at the Apex
fruit types and seed dispersal
The term
true fruit
Is used to refer to fruits containing only ovarian tissue and
accessory fruit
or
false fruit
Is used if any non-ovarian tissue is present.
If the fruit develops from a single ovary or the fused ovaries of one flower, it is a
simple fruit
.
If the separate carpels of one gynoecium fuse during development, an
aggregate fruit
results.
Fruits can be grouped or classified in several ways. In one method, emphasis is placed on whether the fruit is dry or fleshy
A
dry fruit
Is one that is not typically eaten by the natural seed distributing animals
The further classification of dry fruit emphasizes fruit opening.
dehiscent fruit
Break open and release the seeds, whereas
indehiscent
do not.
A
fleshy fruit
Is one that is eaten during a natural seed distribution process.
