6: Perpetuation of Life Flashcards by Lei Lei

Plants reproduce through three types

asexual, sexual, and vegetative

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Offsprings are produced from the vegetative unit produced by a parent without any fusion of sex cells or gametes.

Asexual Reproduction

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can be seen in unicellular organisms such as yeast or bacteria. The content of the parent cell divides into 2, 4, or 8 daughter cells.

Fission

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bud-like growth formed on one side of the parent cell. As soon as the bud separates from the parent cell, it becomes a whole new organism

Budding

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occurs in filamentous algae. It occurs as a result of accidentally breaking off a filament into many fragments. Each new fragment may give rise to a new organism through cell division

Fragmentation

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occurs in lower plants, such as pteridophytes and byrophytes. During this type of asexual reproduction, special reproductive units develop asexually on the body of the parent.

Spore formation

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These special reproductive units are called

spores

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Here, a vegetative part of the plant, such as the root, stem, leaf, or bud, is detached from the body of the parent and grows into a daughter plant that is independent.

Vegetative Reproduction

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involves the fusion of female and male reproductive cells (gametes).

Sexual reproduction

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gametes contain only half the genetic material (chromosomes) for a new organism to exist.

haploid

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The fusion of gametes

fertilization

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When the zygote undergoes further development, it gives rise to a new individual that is ______.

diploid

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At the beginning stages of sexual reproduction, ______ occurs.

meiosis

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multicellular

Spirogyra

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unicellular

Chlamydomonas

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unicellular algae that is found in freshwater ponds.

Chlamydomonas

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are filaments found in flagellates

Flagella

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When Chlamydomonas undergoes asexual reproduction, it is through

zoospores

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The zygotes then develop a thick wall around itself

zygospores

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A free-floating algae found in freshwater ponds.

SpirogyraSpirogyra

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occurs first when filaments break into smaller fragments. Then, each fragment grows into a new organism by cell division.occurs first when filaments break into smaller fragments. Then, each fragment grows into a new organism by cell division.

Vegetative reproduction by fragmentationVegetative reproduction by fragmentation

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when filaments conjugate to form a ladder-like appearance, starts when two filaments lie very close to each other.

Scalariform conjugation

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The cells of the two filaments connect with each other through a __________

conjugation tube

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these plants live for only one year. The plants that produce seeds and flowers within just one season are termed as annuals

Annuals

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plants that live for two seasons, and complete their life cycles within these two seasons. During the first year, the plant is in a vegetative state. In the second year, the plants produce flowers, fruits, or seeds and then they perish

Biennials

plants that live for several years. The vegetative state of these plants may last from one year to several years. In the year following their vegetative state, they produce flowers, seeds, or fruits

Perennials

perennial plants that reproduce only once during their lifetime and then die

Monocarpic

has a soft stem, and only bears a few leaves. The size and shape of the leaves remain the same. It does not respond to stimuli nor does it produce flowers.

juvenile shoot

has well-developed stems and leaves. The size and shape of the leaves change. It also responds to stimuli and can produce flowers.

adult shoot

The plant's flowering is affected by light

photoperiodism

The plant's flowering is affected by temperature

vernalisation

is when low temperatures occur, and this stimulates the early formation of flowers.

Vernalisation

is the response of the plant to the duration of dark and light per day. This determines its growth and flowering.

Photoperiodism

means a flower has both carpels and stamens

bisexual

means a flower has only a staminate or pistillate

unisexual

a plant hormone that assists in growth and reproduction.

Gibberellin

comprise the calyx.

Sepals

comprise the corolla.

Petals

male reproductive organ of a flower

androecium

female reproductive organ of a flower

gynoecium

Each __________ is made up of distinct layers of cells when mature.

microsporangium

The outermost layer is the ________. It has a middle layer of cells with thin walls.

epidermis

The innermost layer is the _______, which consists of large cells. It nourishes the developing grains of pollen.

tapetum

Microspore mother cells undergo _______.

meiosis

exine is made up of a durable substance called

sporopollenin

The outer layer is the

exine and thin spaces (germ pores)

grows out of the pollen grain through the germ pores.

pollen tube

The inner layer is the

cellulosic wall (the intine)

moves towards the periphery.

microspore

The main part of the ovule is bounded by two coverings

integuments

The ovule is attached to the ovary via a stalk

funiculus

The basal part of the female gametophyte structure

chalaza

contains one or more ovules (megasporangia), which act as future seeds

ovary

develops as a type of projection from the placenta in the ovary.

ovule

Within the nucleus, a single ________ cell becomes larger and it becomes the megaspore mother cell.

hypodermal

This cell undergoes ___________, and then gives rise to four haploid megaspore cells.

meiotic division

The enlarged structure, shaped like an oval and with 8 nuclei, is known as the _______

embryo sac

Cell membranes and nuclei develop around the nuclei, except the two at the center of the sac, which is now termed as the _______

central cell

These are provided with buds which develop into a new plant and are therefore used to carry out vegetative propagation of the plant in the field.

Vegetative Reproduction in Angiosperms

The process by which animals propagate on earth and it is also the process through which genetic materials are transferred to offspring.

Animal Reproduction

The formation of identical twins by the separation of two identical cells in the early embryo is a form of

asexual reproduction

occurs when a new individual is formed from the union of two sex cells, or gametes.

Sexual reproduction

the zygote develops into a new organism.

mitotic division

The _________ are formed in the sex organs, or gonads (the testes and the ovaries), and are haploid.

gametes

The process of sperm formation

spermatogenesis

The process of egg formation

oogenesis

Virgin birth is common in many species of arthropods.

parthenogenesis

Some species are exclusively all female

parthenogenetic

Another variation in the reproductive strategies used by animals is

hermaphroditism

The change from female to male is

protogyny

the change from male to female is

protandry

Recent evidence suggests that the __________ appears to have been highly conserved during the evolution of vertebrate groups.

sex-determining gene (SRY)

commonly occurs among organisms in the ocean, where water allows for the rapid dispersion of sperm or ova towards others of the same species.

External fertilization

is the introduction of the male gamete into the female's reproductive tract.

Internal fertilization

is when the eggs are deposited outside the mother's body after fertilization.

Oviparity

The fertilized eggs are retained within the mother in order to complete their development. The embryos still take all of their nourishment from the egg yolk. The young are thus fully developed when they hatch.

Ovoviviparity

is found in almost all mammals. The young develop within the mother and takes its nourishment directly from their mother's blood, as opposed to egg yolks.

Viviparity

In most cartilaginous fish most fertilization is _____.

internal

In internal fertilization, the male introduces sperm into the female by means of a modified _______.

pelvic fin

In Amphibians, gametes from the males and females are released through the __________.

cloaca

The shells of reptile eggs are _____, and this allows for better withstanding of environmental conditions.

leathery

As the eggs pass through the ________, the glands secrete the egg whites and the hard shells that distinguish bird eggs from reptilian eggs.

oviduct

Most birds are also _______, meaning that they keep a stable body temperature.

homeotherms

the embryo that develops within the cavity filled with fluid is surrounded by a membrane called an amnion.

amniotic eggs

is an extra-embryonic membrane and develops outside of the body of the embryo.

amnion

_______ in females is the cyclic release of an egg from the ovary.

Ovulation

The period of sexual receptivity

estrus

the reproductive cycle is therefore called

estrous cycle

The most primitive mammals, the monotremes, are __________

oviparous

derives its nutrients from the mother's blood, since fetal and maternal blood vessels are in close proximity.

fetus

deduced the classical principles of genetics in 1865. He based his deductions on the results of breeding experiments with peas.

Gregor Mendel

genetic composition

genotype

their physical appearance

phenotype

is the term for the deductions of Mendel.

Mendelian genetics

in the form of meiosis involves the daughter cell inheriting only one member of each chromosome pair.

Cell division

Chromosomes exchange materials during ________, leading to the linked genes' recombination.

meiosis

The first evidence for the existence of enzymes came in 1909, through the study of the disease called ________ The disease results from a genetic defect that results in problems with the metabolism of phenylalanine, an amino acid.

phenylketonuria

who formed the basis for present-day molecular biology.

James Watson and Francis Crick

purines

adenine (A), guanine (G)

pyrimidines

cytosine (C), and thymine (T)

Two strands of DNA can separate to serve as templates for a new strand. This would be specified by base pairing.

semiconservative replication

This process is called semiconservative replication, because one strand is conserved in the

progeny DNA molecule

The enzyme that catalyzes DNA replication

DNA polymerase

going both forwards and backwards

bidirectional

going only one direction

unidirectional

directed by genes.

Protein synthesis

the sequence of nucleotides in a gene in the DNA is copied to the corresponding sequence of nucleotides in mRNA.

transcription

the sequence of nucleotides in the mRNA determines the sequence of amino acids in the proteins.

translation

mediated by RNA polymerase It separates the two strands of the double helix and constructs an mRNA molecule by adding nucleotides one at a time.

transcription

determines the sequence of amino acids in the protein.

translation

Each tRNA has three nucleotides that form an

anti-codon

building blocks of proteins

Amino acids

mRNA

messenger RNA

tRNA

transfer RNA