Cell and Tissue Specialization in Multicellular Organisms

Bigger is commonly better in a predatory-prey environment

Being larger means it's easier to ingest smaller organisms; larger organisms are harder for smaller organisms to ingest.

Bigger can also be harder

As organisms become larger, physics starts to work against them; cell surface is used for diffusion of gases, nutrients, and wastes.

Metabolism

Consumes oxygen and nutrients, generates carbon dioxide and wastes.

Surface area to volume ratio

As size increases, the ratio between volume and surface area decreases.

Multicellular Organism

Defined by the formation of cell colonies followed by the specialization of cell functions.

Sponge

Was the first animals in the fossil record to show multicellular organization.

Anatomical organization

Based on the types of cells involved; tissues are made up of multiple cells, organs are made up of multiple tissues, organ systems are made up of multiple organs.

Multicellular Life

Cells within colonies began to specialize to carry out specific tasks at some point of evolution.

Specialization in multicellular organisms

Occurs when cell colonies have each reached a level of specialization which causes them to rely on each other.

Challenges faced by multicellular organisms

Must withstand environment, protect cells, have enough surface area for diffusion, and transport substances around the inside.

Types of tissue cells

Four types: epithelial, connective, muscle, nervous.

Epithelial tissues

Barriers with specially-designed functions.

Skin

A barrier to the outside world, waterproofing, rapid injury response, immunity.

Small intestine

Barrier to intestinal contents, digestion and absorption of nutrients, immunity.

Blood vessel wall

Barrier between blood and tissue, site for gas/fluid exchange, carries immune cells to the entire body.

Connective tissues

Provide gravitational strength and support, movement.

Loose connective tissue

Semi-fluid, flexible; cushions, lubricates, and insulates other tissues.

Dense connective tissue

Tightly packed with many collagen fibers; connects bones to muscles and other bones (e.g., tendons and ligaments).

Bone

Has two major components to accommodate complex loading: collagen and calcium hydroxyapatite.

Osteocytes

Keep up extracellular matrix in bone.

Osteoblasts

Replenish cells in bone.

Osteoclasts

Resorb calcium in bone.

Central canal

Carries blood, lymph, and nerves in bone.

Muscle tissue

Involved in voluntary movement, pumping blood, and movement of materials.

Skeletal muscle

Voluntary muscles that attach to bones and produce movement.

Cardiac muscle

Only found in the heart, automatic; wraps around each of the chambers of the heart.

Smooth muscle

Involuntary; regulates organ function by contracting and relaxing to change the shape of organs.

Nervous tissues

Involved in awareness, movement, sensation, and control of homeostasis.