Download Classification

Organisms and their
Classification
Organisms
• Organisms are living things that are made up of cells.
They share 6 important characteristics. They have
cellular organization, contain similar chemicals, use
energy, respond to their surroundings, grow and
develop, and reproduce.
Cells
• A cell is a basic unit of structure and function in an
organism.
• Unicellular, or single-celled, organisms include
bacteria, the most numerous organisms on Earth.
• Multicellular organisms are composed of many cells.
• The cells of organisms use energy to grow and repair
injured parts.
Prokaryotic vs Eukaryotic
• The difference between prokaryotic and eukaryotic is
considered to be the most important distinction
among groups of organisms. Eukaryotic cells contain
membrane-bound organelles, such as the nucleus,
while prokaryotic cells do not.
• Prokaryotes were the only form of life on Earth for
millions of years until more complicated eukaryotic
cells came into being.
Prokaryotes vs Eukaryotes
Classification
• Classification, or taxonomy, is a system of
categorizing living things. There are seven divisions in
the system: (1) Kingdom; (2) Phylum or Division; (3)
Class; (4) Order; (5) Family; (6) Genus; (7) Species.
• Today, a three-domain system of classification is
commonly used. The three domains are Bacteria,
Archaea, and Eurarya.
• Within the domains are kingdoms.
Domains and Kingdoms
• Kingdom is the broadest division. While scientists
currently disagree as to how many kingdoms there
are, most are now leaning toward a six-kingdom
(Animal, Plant, Protista, Archeabacteria, Eubacteria,
and Fungi) system. The lowest division is species,
which consists of organisms that are capable of
interbreeding to produce fertile offspring.
• Organisms are placed into domains and kingdoms
based on their cell type, their ability to make food,
and the number of cells in their bodies.
Bacteria
• Members of the domain Bacteria are prokaryotes.
• Prokaryotes are single-celled organisms whose cells
lack a membrane-bound nucleus, mitochondria, or
any other membrane-bound organelle. A nucleus is
a dense area in a cell that contains nucleic acids – the
chemical instructions that direct the cell’s activities.
• In prokaryotes, nucleic acids are scattered
throughout the cell. Their DNA is kind of floating
around in the cell – in the cytoplasm.
• Most bacterial cells are surrounded by a rigid cell
wall that helps protect the cell. The cell wall is the
target for antibiotics, as well as for carbohydrates
that our immune system uses to detect infection.
Bacteria
• Some bacteria have flagella. A flagellum is a long, whip
like structure that extends from the cell membrane and
out through the cell wall. This helps the cell move.
• Bacteria must have a source of food and a way of
breaking down the food to release its energy
(respiration).
• Some bacteria are autotrophs and make their own food.
Others are heterotrophs that obtain food by consuming
autotrophs or other heterotrophs.
• Prokaryotic cells come in multiple shapes: cocci (round),
bacilli (rods), and spirilla or spirochetes (spiral).
Prokaryotic Cell
Bacteria
• When bacteria have plenty of food, the right
temperature, and other suitable conditions, they thrive
and reproduce frequently.
• They can reproduce by binary fission – a process in
which one cell divides to form two identical cells (asexual
reproduction – one parent and identical offspring to
parent).
• Others can reproduce by conjugation – a process in
which two parents combine genetic material to produce
a new organism that differs from both parents (sexual
reproduction).
Bacteria
• Many bacteria can survive harsh conditions by forming
endospores. Endospores are small, rounded, thickwalled, resting cells that form inside a bacterial cell.
• Some bacteria cause diseases and other harmful
conditions. However – most are harmless or helpful to
people. Bacteria are involved in oxygen and food
production, environmental recycling and clean-up, and
health maintenance/medicine production.
• Helpful bacteria produce foods (cheese & pickles).
Others actually cause food to spoil. To combat spoilage –
food can be heated to a temperature that will kill the
bacteria (pasteurization).
Bacteria
• Heterotrophic bacteria in the soil break down materials
for reuse. These bacteria are decomposers – organisms
that break down large chemicals in dead organisms into
small chemicals.
Archaea
• Members of the domain Archaea, whose name comes from
the Greek word for “ancient”, can be found in some of the
most extreme environments on Earth, including hot springs,
very salty water, swamps, and the intestines of cows.
• Scientists think that the harsh conditions in which archaea live
are similar to those of ancient Earth.
• Like bacteria, some archaea are unicellular prokaryotypes and
some are autotrophs while others are heterotrophs.
• Although bacteria and archaea are similar in some ways, there
are important differences in the structure and chemical makeup of their cells.
Eukarya
• Members of the domain Eukarya are eukaryotes –
organisms with cells that contain nuclei.
• Scientists classify organisms in the domain Eukarya into
one of four kingdoms: plants, animals, protists, and
fungi.
• Plants are all multicellular eukaryotes. In general, plants
are autotrophs and feed almost all of the heterotrophs
on land.
• Animals are multicellular eukaryotes. All animals are
heterotrophs. Animals have different adaptations that
allow them to find food, capture it, eat it, and digest it.
Protista
• The protista kingdom is sometimes called the “odds and
ends” kingdom because its members are so different
from one another. All protists are eukaryotes that cannot
be classified as animals, plants, or fungi.
• All live in moist surroundings. Slime molds are protists.
• Protists can be autotrophs or heterotrophs. Some can be
both!
• Although many protists are unicellular, some, such as
seaweeds, are multicellular. Protists can be divided into
three categories: animal-like, plant-like, and fungus-like.
Animal-like Protists
• Animal-like protists are heterotrophs, and most are able
to move from place to place to obtain food. They can
also be called protozoans.
• Some animal-like protists survive by symbiosis – a close
relationship between two species where at least one of
the species benefits.
• Other animal-like protists survive by mutualism – in
which both partners benefits.
• Parasites (a type of animal-like protist) feed on their
hosts’ cells and body fluids.
Plant-like Protists/Fungi
• Plant-like protists are called algae. Algae are autotrophs.
Algae can exist in a variety of colors because they contain
many types of pigments – chemicals that produce color.
• Fungus-like protists are heterotrophs, have cell walls, and
use spores to reproduce. Spores are tiny cells that are
able to move at some point in their lives.
Protists
Fungi
• Fungi are eukaryotes that have cell walls, are
heterotrophs that feed by absorbing their food, and
use spores to reproduce. They need warm, moist
places in which to grow. Fungi are found almost
everywhere on land, but only a few live in fresh
water.
Fungi
• A few fungi, such as yeast, are unicellular eukaryotes.
Most fungi are multicellular eukaryotes. Hyphae are
branching, threadlike tubes that make-up the bodies.
What a fungus looks like depends on the
arrangement of its hyphae.
• First, the fungus grows hyphae into a food source.
Then digestive chemicals ooze from the hyphae into
the food. The digestive chemicals break down the
food into small substances that can be absorbed by
the hyphae. Some fungi feed on the remains of dead
organisms. Others are parasites that break down the
chemicals in living organisms.
Fungi
Fungi
• Fungi usually reproduce by making spores. The
lightweight spores are surrounded by protective covering
and can be carried easily through the air or water to new
sites.
• Spores are produced in reproductions structures called
fruiting bodies.
• Unicellular yeasts use a form of asexual reproduction
(identical to the parent) called budding. In budding, a
small cell grows from the body of a large, well-fed cell.
• Sexual reproduction can occur when the hyphae of two
fungi grow together and new genetic material is
exchanged.
Important Info about Fungi
• They play an important roles as decomposers and
recyclers on Earth. (by breaking down the chemicals in
dead organisms)
• They provide foods for people. (yeast, mushrooms, etc.)
• They cause disease AND fight disease. (penicillium)
• They live in symbiosis with other organisms. (The hyphae
of some fungi grow among the roots of plants –
absorbing water and nutrients from the soil. In return,
the fungus feeds on the extra food the plant makes.)
• A lichen consists of a fungus living in a mutualistic
relationship with algae or autotrophic bacteria.
The Plant Kingdom
• Most plants are autotrophs. All plants are eukaryotes
that contain many cells. All plants’ cells are surrounded
by a cell wall.
• Most plants live on land. For plants to survive on land,
they must have ways to obtain water and other nutrients
from their surroundings, retain water, transport materials
within their bodies, support their bodies, and reproduce.
• Plants make their own food by photosynthesis. They use
carbon dioxide gas and water to make food and oxygen.
The Plant Kingdom
• Plant cells are organized into tissues, groups of similar
cells that perform a specific function.
• Some plants have vascular tissue, a system of tube-like
structures inside the plant through which food, minerals,
and water move. Vascular tissue also provides strength,
stability, and support to a plant. These plants can grow
quite tall.
• Nonvascular plants do not have a well-developed system
of tubes for transporting water and other materials.
They grow low to the ground.
The Plant Kingdom
• All plants undergo sexual reproduction that involves
fertilization. Fertilization occurs when a sperm cell
unites with an egg cell. The fertilized egg is called a
zygote.
• Plants have complex life cycles that include two different
stages, the sporophyte stage and the gametophyte stage.
• In the sporophyte stage, the plant produces spores, tiny
cells that can grow into new organisms. A spore
develops into the plant’s other stage, called the
gametophyte stage. In this stage, the plant produces two
kinds of cells: sperm cells and egg cells.
Autotrophs vs Heterotrophs
Autotrophs
• Autotrophs are organisms that can produce their own
food from the substances available in their surroundings
using light (photosynthesis) or chemical energy
(chemosynthesis).
• An autotroph is an organism that is able to form
nutritional organic substances – ex: plants, algae, and
some bacteria.
• They are often called “self feeders” or “primary
producers” that obtain carbon from inorganic sources
like carbon dioxide (CO2).
Heterotrophs
• Heterotrophs cannot make their own food and rely
on other organisms – both plants and animals – for
nutrition.
• Heterotrophs get their reduced carbon from other
organisms.
• Basically – heterotrophs depend on autotrophs and
other heterotrophs.
• Herbivores, omnivores, and carnivores are all
heterotrophs.
Food Chain
Food Chain
• Autotrophs are primary producers that are placed
first in the food chain.
• Heterotrophs that depend on autotrophs and other
heterotrophs for their energy level are placed next
on the food chain.
• Herbivores that feed on autotrophs are placed in the
second trophic level. Carnivores that eat meat and
omnivores that eat all types of organisms are placed
next in the tropic level.