Plants and Humans Test 2

What are the two main sources of information that plants perceive?

External environment and internal plant body.

What are some environmental stimuli that affect plant growth?

Gravity, touch, temperature, light, and chemicals.

How do plants detect gravity?

Through statocytes, which are gravity-sensing cells that contain statoliths (starch grains).

What is the role of hormones in plant responses?

Hormones are produced in small amounts in one part of the plant and moved to another part to trigger responses, often disproportionate to the hormone amount.

What is the function of auxin in plants?

Auxin promotes cell elongation, apical dominance, and the formation of adventitious roots from cuttings.

What does cytokinin do in plants?

Cytokinin stimulates cell division and activates dormant buds.

What is the role of abscisic acid (ABA) in plants?

ABA is involved in stress responses.

What is the function of gibberellins (GA) in seed germination?

Gibberellins promote seed germination.

What role does ethylene play in plants?

Ethylene is responsible for fruit ripening.

What are the steps involved in seed germination?

1. Embryo takes in water and swells. 2. Embryo secretes gibberellin into the aleurone layer, producing enzymes. 3. Enzymes move into the endosperm. 4. Enzymes digest the endosperm to provide nutrients for the embryo.

What is the significance of adaptive changes in plants?

Adaptive changes allow plants to respond to environmental stimuli effectively.

How do plants transfer information to other parts?

Through hormones that signal responses from different sites.

Why do plants not have complex sensory organs?

Plants rely on simpler mechanisms to perceive environmental stimuli.

Tropic responses

Growth-oriented responses to a stimulus that can be positive (toward), negative (away), or at an angle to the stimulus; involve differential growth and permanent change.

Nastic responses

Temporary expansion/shrinkage of cells, reversible change; not oriented with regard to stimulus.

Morphogenic response

Change in development or quality in plant.

All-or none response

No response until a stimulus has acted for a certain time or reached a critical strength; e.g. Venus flytrap.

Dosage-dependent response

Response depends on dose of the stimulus; e.g. day length and flowering.

Etiolation

Seedling growth in the dark; etiolated form has little or no chlorophyll, tiny undeveloped leaves, and long slender internodes - an adaptive growth form.

Phototropism

Shoot bends toward the brighter side of the light due to redistribution of auxin, differential growth, and bending; first studied in oat coleoptiles.

Gravitropism

Roots, rhizomes, and subterranean organs orient using gravitropism; statoliths settle to the downward side of the statocytes, causing differential growth.

Apical Dominance

Suppression of uppermost buds by growing shoot apex; auxin produced by the shoot apex suppresses buds closer to the apex.

Fruit Ripening

Can be a slow process, initially slow and then rapid; climacteric ripening involves ethylene, which induces production of more ethylene.

Climacteric ripening

Involves ethylene (e.g. banana); can be harvested while immature and induced to ripen by artificially treating with ethylene.

Non-climacteric ripening

Produces little or no ethylene (e.g. grapes).

Asexual reproduction

A single parent produces offspring that are genetically identical to parent, faster than sexual reproduction.

Example of Asexual reproduction

Vegetative propagation.

Sexual reproduction

Each parent produces gametes, which join to create offspring and have genetic diversity.

Vegetative Propagation

A parent plant forms a creeping stem that begins rooting and forms a new plant.

Example of Vegetative Propagation

Strawberry plants.

Cell Cycle

The life of the cell from one division to the next.

Parts of the Cell Cycle

3 primary parts: interphase, cell division, and cytokinesis.

Interphase

Cells grow and copy their DNA.

Cell/Nuclear division

Division of the DNA in the nucleus.

Cytokinesis

Cytoplasm divides.

Longest part of the cell cycle

Interphase.

G1 phase

Cell growth.

S (synthesis) phase

DNA is replicated/copied.

G2 phase

More cell growth.

Mitosis

One type of cell/nuclear division, associated with asexual reproduction, occurs in body cells.

PMAT

Stages of mitosis: prophase, metaphase, anaphase, telophase.

Chromatin

DNA and protein (plate of spaghetti).

Chromosomes

Condensed chromatin (single noodle).

Sister chromatids

Duplicated chromosomes (two noodles arranged in an X shape).

Prophase

Chromatin condenses to form visible X-shaped sister chromatids; nucleolus disappears; nuclear envelope starts breaking down; spindle forms.

Metaphase

Sister chromatids attach to the spindle and line up in the middle of the cell.

Anaphase

Sister chromatids separate (now called chromosomes).

Telophase

Chromosomes reach the opposite ends of the cell and start to unravel into chromatin; spindle disappears; nuclear envelope reappears; nucleolus reappears.

What is the process called that involves a swap between a sexual phase and an asexual phase in the life cycle of plants?

Alternation of generations

What phase of the plant life cycle is haploid and produces gametes through mitosis?

Gametophyte

What is formed when an egg and sperm unite in the plant life cycle?

Zygote (diploid)

What does the zygote develop into after many rounds of mitosis?

Sporophyte (diploid)

What process does the sporophyte undergo to produce haploid spores?

Meiosis

What is the unique fertilization process found in angiosperms?

Double fertilization

In double fertilization, what does one sperm fertilize and what does the other sperm fertilize?

One sperm fertilizes the egg, and the other fertilizes two polar nuclei to form triploid endosperm.

What is a population in biological terms?

Individuals of the same species living in the same place at the same time.

What is a gene pool?

All the alleles of every individual in a population.

What is genetic drift?

A random change in allele frequency, often occurring in small populations.

What is artificial selection?

The purposeful change of allele frequency of a gene pool by humans.

What is natural selection?

The process where individuals with advantageous traits are more likely to survive and reproduce.

What conditions must be met for natural selection to occur?

1) More offspring must be produced than can survive. 2) Progeny must differ in their allele types.

How does population change occur?

Population change is usually slow but can sometimes be rapid.

What defines a species?

Organisms that can interbreed and produce fertile offspring.

What is speciation?

The evolution of species through natural selection.

What is allopatric speciation?

Speciation that occurs due to geographic separation.

What is sympatric speciation?

Speciation that occurs when species remain in the same place.

What is divergent speciation?

When species share a recent common ancestor but evolve into different species.

What are homologous structures?

Anatomical features that share a common ancestry but have different functions, such as bat wings and human arms.

Give an example of divergent speciation.

Species A evolves into Species B and Species C, which have different adaptations.

Adaptive Radiation

A form of divergent evolution where a species rapidly diverges into many new species over a short period of time.

Conditions for Adaptive Radiation

Occurs when there is no competition or environmental stress.

Example of Adaptive Radiation

Newly formed islands or sudden environmental changes that eliminate dominant species.

Convergent Evolution

Natural selection favors some phenotype when two unrelated species occupy the same or similar habitats.

Analogous Structures

Structures like dolphin flipper and shark fin that have no shared ancestry but similar function.

Example of Convergent Evolution

Cacti (Americas) and euphorbias (Africa) resemble each other in appearance.

Taxonomy

The classification of organisms into categories such as Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Scientific Name

Consists of genus and species, for example, Magnolia grandiflora.

Taxon

Used to refer to any taxonomic levels.

Three Domains

Bacteria, Archaea, Eukaryota/Eukarya.

Six Kingdoms

Eubacteria, Archaebacteria, Plantae, Animalia, Fungi, Protista.

Phylogenetic Trees

Diagrams that show evolutionary relationships.

Cladogram

A diagram that shows the development of characteristics by means of a series of branches.