Organisms as Systems

Organisms as systems

Introduction

Organisms have a wide range of responses to their environments. These responses are made possible through the cooperation of body systems. A cell is the simplest level of organization in an organism. Just like the organism as a whole, a cell is a system.

Levels of Organization in Organisms

All living things are organized. Each living thing is a system that performs all the life processes needed for survival. Some living things are made up of multiple subsystems. Other living things are a system of only a single cell.

Cells: Unicellular organisms have one level of organization. All the functions needed for life are performed by one cell. Multicellular organisms are made up of more than one cell.

A protozoan is unicellular. This Amoeba proteus moves and engulfs prey by using extensions of its body.

Oak trees are multicellular. They have many leaves to capture sunlight, and a specialized stem called a trunk.

E.coli bacteria are unicellular. They have whip-like structures that help them move and attach to host cells.

The Eurasian water shrew is multicellular. It uses its sensitive whiskers to hunt snails and aquatic insects underwater.

Tissues

In organisms, such as plants and animals, specialized cells are grouped together in tissues that are organized to perform a specific function.

Organs

Different types of tissues that function together form an organ.

We know it all starts with the cell. And for some species it ends with the cell. But for others, the cells come together to form tissues, tissues form organs, organs form organ systems, and organ systems combine to form an organism.

Body Systems

Organisms need to process nutrients and take in oxygen. They need to move to find food and mates, avoid predators, and travel to warmer temperatures. In multicellular organisms, body systems work together to perform functions. The coordination of systems gives an organism a greater variety of possible functions and responses.

Sailfish are the fastest fish in the ocean. They travel to the Gulf of Mexico from late January to March to feed on sardines. These sailfish are working together to hunt the school of sardines.

Exploring Plant Body Systems

Plants live on every continent on Earth. They live in places such as lush forests and expansive grasslands. They also live in places you might not expect, such as dry deserts and frozen tundra. They range in size from the tallest giant sequoia trees, reaching more than 80 meters, to the smallest flowering plant, which can fit on the tip of your finger.

All plants are multicellular. They are also eukaryotes—their cells contain membrane-bound organelles, including a nucleus that contains the cell’s genetic information. All plants have cell walls and large vacuoles. All plants convert the energy from sunlight to food energy by process called photosynthesis .

The root system of the saguaro cactus is shallow, but it reaches out as far as the plant is tall.

The water lily’s broad, flat leaves float on the water to maximize the amount of sunlight they can capture.

This maple tree has a central stem, called a trunk, that connects the roots to the branches of the tree.

Plant Body System

Plants can be divided into two major groups, based on the structure and function of their body systems. Plants that have a vascular system are called vascular plants . Plants that do not have a vascular system are called nonvascular plants .

Plants with Vascular system

Vascular plants are plants that use specialized tissue for transporting food and water to different areas in the plant. Examples of vascular plants include trees, flowers, grasses and vines.

Vascular Plants Characterisitcs

Roots: are simple tissues that are derived from the stem of the plant. Roots anchor the plant in the ground and transport minerals and water into the plant.

Xylem: is tissue that transports water throughout the plant. It can be found throughout the plant, in the roots, stem and leaves.

Phloem: is the plant's food transportation system. They bring minerals up through the roots and the byproducts of photosynthesis down to move them throughout the plant.

Leaves: are two types of leaves for vascular plants: microphylls and megaphylls. Microphylls have one vascular strand where all the vascular tissue runs parallel in the leaf. Megaphylls have branching vascular tissue within the leaf.

The primary growth of the plant occurs at the tips of the roots and the stems, lengthening the vascular system. Secondary growth thickens the stem and the roots, making them wider.

Non-Vascular Plants

Most bryophytes are small. They not only lack vascular tissues; they also lack true leaves, seeds, and flowers. Instead of roots, they have hair-like rhizoids to anchor them to the ground and to absorb water and minerals They include liverworts, hornworts, and mosses.