Multicellularity, Development, Reproduction

Physiological challenges of large cell size

Increased distance for nutrient and waste transport, slower metabolic rates, and difficulty exchanging materials with the environment.

Adaptations for large cell size

Development of specialized organelles that compartmentalize functions, enhancing metabolic efficiency.

Function of multicellularity

Allows for division of labor among cells, leading to specialization in tasks like nutrient absorption, waste elimination, and reproduction.

Significance of signaling mechanisms in multicellularity

Evolved to coordinate activities among cells to maintain homeostasis.

Constraint on cell size

As cells become larger, the surface-area-to-volume ratio decreases, complicating nutrient and waste exchange.

Cell geometry in eukaryotes

Some eukaryotic cells are long and thin to increase surface area for better nutrient exchange.

Reproduction strategy under cell size constraint

Cells divide through mitosis when they become too large to maintain efficiency.

Internal complexity in eukaryotic cells

Presence of organelles that compartmentalize functions for specialized tasks.

Five essential developmental processes in eukaryotes

Cell proliferation, programmed cell death, cell movement, cell differentiation, and cell-cell interaction.

Role of cell proliferation

Reproduction of new cells via mitosis, critical for growth and adding new cells.

Programmed cell death

Specific death of cells necessary for proper development and tissue shaping.

Differential cell movement

Movement of cells to new locations; differs between animals (cell movement) and plants (cell expansion).

Morphogen

Signaling molecule that influences the identity of cells based on its concentration gradient.

Induction in cell differentiation

Cell-to-cell communication from surrounding cells alters gene expression in developing tissues.

Reproductive strategies in fungi

Include equal or multiple fission, budding, spores, and fragmentation.

Reproductive strategies in animals

Include budding, parthenogenesis, polyembryony, and fragmentation.

Reproductive strategies in plants

Include spores, fragmentation, vegetative growth, parthenogenesis, and polyembryony.

Asexual reproduction

Involves reproduction without the fusion of gametes, resulting in genetically identical offspring.

Budding in asexual reproduction

A process where a small organism grows off a parent organism and eventually detaches.

Fragmentation in asexual reproduction

A type of reproduction where a piece of the organism can grow into a new individual.

Parthenogenesis

Development of an offspring from an unfertilized egg.

Polyembryony

A mode of reproduction where a fertilized egg splits to form genetically identical clones.

Vegetative growth

Growth of new organisms from meristematic cells without the need for gametes or spores.

Cost of sexual reproduction

Includes time and energy spent finding a mate, and potential risks of unpredictable offspring.

Two-fold cost of sex

In sexual reproduction, only females produce offspring, leading to fewer total offspring compared to asexual reproduction.

Advantages of asexual reproduction

Produces more offspring quickly and efficiently under stable conditions.

Disadvantages of asexual reproduction

Offspring are genetically identical, which can be a disadvantage in changing environments.

Three types of life cycles in eukaryotes

Haplontic, diplontic, and alternation of generations.

Haplontic life cycle

The mature organism is haploid; produces gametes via mitosis, then undergoes meiosis to produce spores.

Diplontic life cycle

The mature organism is diploid; gametes are produced via meiosis that fuse to form a diploid zygote.

Alternation of Generations

Includes both haploid and diploid multicellular stages; gametophyte and sporophyte alternates.

Gametogenesis

The process of making gametes that occurs in sexual reproduction.

Importance of fertilization

Fusing gametes into a single-cell zygote is critical for sexual reproduction.

Spore characteristics

Spores are haploid and can develop into a new organism, unlike gametes.

Zygote characteristics

A diploid cell formed from the fusion of haploid gametes, which develops into a multicellular organism.