Honors Bio 2 chapter 26

What is coenocytic organization

An organism where the nucleus divides multiple times, but the cytoplasm does not , resulting in a large cell

What is cell adhesion

Molecules that cause adjacent cells to stick together, with little communication or transfer of resources between cells and little differentiation of specialized cell types (cells must stick together)

What is cell communication

Cells being able to communicate with one another

What is genetic programs

Cells participating in a network of genetic interactions for cell division and differentiation

What is bulk flow

Molecules moving at rates beyond those possible by diffusion across a concentration gradient

What is diffusion

Random motion of molecules with net movement from areas of higher to lower concentration

What is surface area to volume ratio

A necessary trait for cells to effectively transport molecules, with a high ratio making it easier

What are choanoflagellates

Single celled eukaryotes closely related to animals due to them having cell adhesion and cell signaling (contains genes that code for Cadherin and integrin proteins)

What is a meristem

Specific regions of growth in plants, found at the tips of roots and stems (due to cell wall and growth by division, expansion, and differentiation)

What is a blastula

A hollow, fluid filled ball of cells that develops from the morula and is an early stage of embryo development in animals

What is a gastrula

A stage of early embryo development in animals when cells of the hollow blastula migrate and reorganize to form a multilayered structure in which different cell types begin to differentiate

How many groups of eukaryotes are multicellular

36 out of 119

What are the other 83 groups of eukaryotes

Single celled organisms that eat other microorganisms or small organic particles, live suspended in water columns, or are parasites living within other organisms

Where do simple multicellular organisms originate

From colonial organisms, which stuck together for reproduction and feeding

What are traits of simple multicellular organisms

They contain adhesion molecules to allow cells to stick together, despite little communication, resource transfer, or differentiation, each cell has a full range of functions, and every cell is in contact with the environment for diffusion

What is an advantage of being multicelllular

Avoiding predation as predators cannot focus on one cell

What occurs in organisms with coenocytic organization

They are one large cell with multiple nuclei ass the cytoplasm does not divide, sometimes visible to the naked eye

What are the cons of multicellularity

Higher energy costs to develop, grow, and maintain tissues

Different functions require cells to cooperate (due to specialization during development using protein gradients)

Opportunities for individual cells to use resources to grow themselves and not the rest of the organism (cancer)

What does complex multicellularity require

Cell adhesion, cell communication, and genetic programs

What is three-dimensional organization

Multicellular organisms that have some cells in direct contact with the environment, meaning they need mechanisms for transferring environmental signals received by surface cells to interior cells, where genes will be activated in response

How many times did complex multicellularity evolve

6 times, once in animals, in green algae (leading to vascular plants), red algae, brown algae, and fungi twice

What is a key challenge of complex multicellularity

Transporting food, oxygen, and molecular signals rapidly across large distances within the body and exporting waste products out of the body

How are small distance limits via diffusion overcame by animals

A sponge places active cells close to the environment by using pores and canals

Jellyfish have thin layers of tissue, but have a thick shape due to inactive molecules

Animals have a high ratio of surface area to volume ratio in some cells, and use bulk transport

What are examples of bulk flow

Animals pumping blood through the circulatory system to oxygenate tissues far away, digestion, or hormone signaling

Trees transport water upward from their roots

Fungi transport nutrients through long filaments, relying on osmosis to get from absorption sites to metabolism sites

Why is cell adhesion important in development

A fertilized egg must divide many times and the cells produced must stick together

What are Cadherins integrins

With other transmembrane proteins, they provide mechanisms for adhesion in animal cells

What are pectins

Adhesion molecules in plants (where jelly comes from)

How do cells communicate

A signaling molecule from one cell binds with a receptor on the second cell, causing a change in gene expression, found in animals, plants, and some protists

What are gap junctions

Protein channels that allow ions and molecules to move from one cell to neighboring cells, allowing for targeted communication between them

What is a plasmodesmata

Small openings in a cell wall that allow plant cells to transport materials to other cells despite the wall

What is genetic programming

Cells differentiating in space during development, forming a three dimensional multicellular organism, instructions needed for complex multicellularity

How does genetic programming work

Cells have different fates based on what genes are activated or their spatial position, using many genes and gene families to determine the fate of the cell

What do gene families do

They play key roles in multicellular development, especially hox genes for position

In unicellular organisms, they play a role in differentiation in life cycle stages

How does three dimensional development effect cells

Because interior cells are in a different chemical and physical environment with less nutrients, oxygen and light, there is a gradient of environmental signals, that when controlled genetically, led to complex development

What is true about the development of plants and animals

Complex multicellularity evolved independently in each group

How does plant multicellularity be unique

The cell wall limits cell movement, but growth still involves division, expansion, and differentiation, so plant growth is confined to meristems

How does plant development work

Site specific cell division, followed by differentiation into distinct cell types that govern the function of the whole plant

What is a unique part of plant development

Due to their lack of moving parts, they had to evolve to transport water and nutrients via adjusting to environmental signals by adjusting meristem activity, as well as mechanisms of defense like hairs and spines

What makes animal multicellularity different from plants

Due to no cell walls, they can move, such as blastula cells moving to form a gastrula, leading to the gastrula bringing new populations of cells into contact, leading to signaling and regulation that begins growth and specification

What do gradients in signaling molecules do in multicellular animals

They define directions in animals during development

How does animal cells not having cell walls effect it

It allows for them to form organs with moving parts such as muscle for moving food and fluids, as well as the organism itself allowing it to escape challenge

How did complex multicellularity evolve

Natural selection favored an increase and diversification of genes for growth and development, leading to complex organisms

What to phylogenetic trees show about the development of complex multicellularity

Cell signaling, then adhesion, then plasmodesmata, and bulk transport in plants

In animals, cell adhesion and signaling, gap junctions, and bulk transport

How does oxygen help with complex multicellularity

It is the only molecule that occurs in sufficient concentrations to be a useful electron receptor, and oxidizing organic molecules provides energy to support large organisms

What is true about the increased presence of oxygen

As oxygen in the atmosphere increased, more complex organisms