Chapter 22 Protists
Chapter 22: Protists
22-1: Characteristics of Protists
Protists Are a Varied and Ancient Group of Organisms
Protists are the most diverse of all organisms - most are unicellular - microscopic - few are complex and multicellular
Characteristics
- eukaryotes - some photosynthesis - some ingest their food - some absorb their food - some have flagella or cilia o used for locomotion or getting food - found almost everywhere there is water - damp soil and sand - some are parasitic - most have mechanisms for monitoring and responding to their environment - some have eyespots o small organelles containing light-sensitive …show more content…
pigments that detect changes in light
The first eukaryotes
The first eukaryotes are thought to have evolved about 1.5 bya through the process of Endosymbiosis. This kingdom gave rise to the three kingdoms of multicellular organisms – fungi, plants and animals.
There are two important features that evolved among the protists 1.
sexual reproduction 2. multicellularity
Many protists reproduce only asexually – mitosis. Some use meiosis and sexual reproduction only in times of stress and then others reproduce sexually most of the time.
What unites protists?
The kingdom Protista contains all eukaryotes that don’t fit in animals, plants and fungi.
See table on page 479 for distinguishing one phyla of protists from another.
Generally protist that are heterotrophic are called protozoan and photosynthetic protists are called algae.
Protists Reproduce Sexually and Asexually
Typically unicellular protists reproduce by forming complex colonies. Chlamydomonas species reproduce sexually and asexually. The single-celled protist is haploid and reproduces asexually by absorbing its tail and dividing by mitosis. Mitosis produces two to eight haploid cells called zoospores. Many zoospores break out of the parent cell and grow to become mature haploid cells.
Sexual reproduction among unicellular protists
During environmental stress certain protists reproduce sexually - haploid cells divide by mitosis producing haploid gametes - a pair of gametes fuse to form a …show more content…
pair - this pair sheds their cell wall and fuse into a diploid zygote o zygospore (thick protective wall) can withstand unfavorable conditions
Sexual reproduction among multicellular protists
There are a variety of ways in which protists reproduce sexually: 1. alternation of generations – two distinct multicellular phases a. sporophyte generation – diploid (spore producing phase) i. reproductive cells called sporangia produce haploid spores by meiosis b. gametophyte generation – haploid (gamete producing phase) i. produce gametophyte haploid gametes that fuse divide through mitosis 2. conjugation- the temporary union of two protists to exchange nuclear material a. two filaments align side by side b. cell walls form a bridge between the cells c. the nucleus of one then passes through the tube into the other cell d. the two nuclei form a resting spore e. producing an new haploid
22-2: Protists Diversity
Protists Can Move by Using Cytoplasmic Extension
Amoebas and forams are unicellular heterotrophs that have a unique form of movement.
Ameobas – phylum Rhizopoda - move by using flexible, cytoplasmic extensions – pseudopodia - extremely flexible, no cell wall - pseudopodia surrounds and engulfs food particle - live in freshwater and salt water - reproduce by binary fission – dividing into two new cells - most free-living, some parasitic
Forams – phylum Foraminifera - marine protists - live in sand or attach themselves to other organisms or rocks - porous shells – tests - have many chambers arranged in a spiral shape - cytoplasm extends through the pores in the test to aid in swimming and catching prey - have symbiotic relationship with algae - dead accumulate on ocean floors to form limestone deposits
Diatoms Have Double Shells
Diatoms – phylum Bacillariophyta - photosynthetic - unicellular protists - unique double shells made of silica - shells like small boxed with lids - abundant in oceans and lakes - important producers - have two types of symmetry o radial – like a wheel o bilateral – mirror image
- shells form diatomaceous earth used as an abrasive or in paint used on roads - natural control for pests - move by secreting chemicals through and gliding across a surface - diploid and usually reproduces asexually – two halves of the shell separate and regenerates o tend to get smaller and smaller
Many Algae Are Multicellular
Some are unicellular, while most are multicellular. Algae are distinguished by the type of photosynthetic pigment they contain and by their cell or body shape.
Green algae – phylum Chlorophyta - freshwater unicellular - some are large, multicellular marine organisms - major part of microscopic marine plankton - live in damp soil or thrive within the cells of other organisms – symbiosis - contain the same pigments found in chloroplasts of plants - have both sexual and asexual reproductive stages
Red algae – phylum Rhodophyta - multicellular - found in warm ocean water - red pigments can absorb the light that penetrates deep waters - some have calcium carbonate in their cell walls - others are used to make agar and carrageenan – ice cream - complex life cycle, usually involving alternation of generations
Brown algae – phylum Phaeophyta - multicellular - found in marine environments - larger know as kelp – grow along coasts and provide food and shelter for many different organisms - among the largest organisms on Earth
Some Protists Move with Flagella
Flagellates are protists that move using flagella. There are three major groups: 1. Dinoflagellates – phylum Dinoflagellata - unicellular phototrophs - most have two flagella - few are found in freshwater - most are marine and make up part of the plankton - have a protective coat made of cellulose and silica – unusual shapes - flagella in two grooves – spin through the water like a top - few produce toxins – red tides - reproduce asexually by mitosis
2. Zoogastigotes – phylum Zoomastigina - unicellular heterotrophs - have at least one flagella, some have thousands - most reproduce only asexually - some produce gametes and reproduce sexually - symbiosis – Trichonympha live in the guts of termites providing an enzyme that digests wood - trypanosomes causes diseases in humans and animals – African sleeping sickness
3. Eugleniods – phylum Euglenophyta - freshwater protists with two flagella - one-third of the 1,000 species of hove chloroplasts – photosynthetic - others lack chloroplast and ingest their food – heterotrophic - Euglena – pellicle = protein scaffold - can change shape - eyespot = light-sensitive organ helps orient the movement toward light - reproduce by mitosis
Ciliates Are Complex Protists That Use Cilia to Swim
Ciliates are the most complex and unusual of the protists.
Ciliates – phylum Ciliophora - have large numbers of cilia = tightly packed rows of short flagella used for movement - complex unicellular heterotrophs - body walls are tough but flexible – can squeeze through or around many obstacles - form vacuoles for ingesting nutrients and regulating their water balance - most have two nuclei o micronuclei = contains normal chromosomes that divide by mitosis o macronuclei – contains small pieces of DNA derived from micronuclei used in routine cellular functions - reproduces by mitosis – splitting in half - can engage in sexual reproduction by conjugation
Protists Molds Are Not Fungi
Protistan molds are heterotrophs with some mobility. They have cell walls made of carbohydrates.
Cellular slime molds – phylum Acrasiomycota - move through soil and digest bacteria - during environmental stress they gather together forming multicellular colonies called slugs - slugs develop a base, a stalk and a swollen tip that develop spores - each spore becomes a new organism and begins to
feed
Plasmodial slime molds – phylum Myxomycota - stream along a mass of cytoplasm that looks like an oozing slime – plasmodium - as they move, they engulf bacteria and other organic material - contain many nuclei but are not separated by a cell wall - when it begins to starve or dry out it divides in order to survive
Other molds – phylum Oomycetes - water molds, white rusts and down mildews - often grow on dead algae and dead animals in freshwater - either parasites or feed on dead organic matter - have two flagella – one pointed forward the other pointed backward - many are plant pathogens – blight in potatoes
Some Protists Form Resistant Stages
Parasitic protists that form spores during reproductive cycle are called sporozoans.
Sporozoans - phylum Apicomplexa - 4,500 species - nonmotile, unicellular - parasites that cause many diseases – Malaria - have complex life cycles that involve both asexual and sexual reproduction - infect animals and are transmitted from host to host - transmitted by another host by blood-feeding insects – mosquitoes, black flies - can be transmitted in the feces of an infected animal - can be transmitted through predation
22-3: Protists and Health
How Do Protists Affect Humanity
One of the greatest effects protists have on humans is that they cause disease. See table on page 490.
Beneficial protists
There are many commensal protists that live in the digestive tracts of humans and in the digestive tracts of the animals that humans eat. Protists are the single largest group of photosynthesizers on the planet. Many protists are detritivores.
Malaria Is Caused by Several Species of Plasmodium
Malaria is one of the most deadly diseases in humans.
Malaria life cycle
Malaria is caused by several species of Plasmodium and is spread by the bite of certain mosquitoes. See page 491 for the life cycle.
sporozoite = the infective stage of Plasmodium
merozoite = second stage of Plasmodium, in which the protist divides rapidly in RBC’s and produces many more merozoites
Treating and preventing malaria
Quinine was discovered to be a remedy for malaria. Reducing the mosquito population can also control malaria.
22-1: Characteristics of Protists
Protists Are a Varied and Ancient Group of Organisms
Protists are the most diverse of all organisms - most are unicellular - microscopic - few are complex and multicellular
Characteristics
- eukaryotes - some photosynthesis - some ingest their food - some absorb their food - some have flagella or cilia o used for locomotion or getting food - found almost everywhere there is water - damp soil and sand - some are parasitic - most have mechanisms for monitoring and responding to their environment - some have eyespots o small organelles containing light-sensitive …show more content…
pigments that detect changes in light
The first eukaryotes
The first eukaryotes are thought to have evolved about 1.5 bya through the process of Endosymbiosis. This kingdom gave rise to the three kingdoms of multicellular organisms – fungi, plants and animals.
There are two important features that evolved among the protists 1.
sexual reproduction 2. multicellularity
Many protists reproduce only asexually – mitosis. Some use meiosis and sexual reproduction only in times of stress and then others reproduce sexually most of the time.
What unites protists?
The kingdom Protista contains all eukaryotes that don’t fit in animals, plants and fungi.
See table on page 479 for distinguishing one phyla of protists from another.
Generally protist that are heterotrophic are called protozoan and photosynthetic protists are called algae.
Protists Reproduce Sexually and Asexually
Typically unicellular protists reproduce by forming complex colonies. Chlamydomonas species reproduce sexually and asexually. The single-celled protist is haploid and reproduces asexually by absorbing its tail and dividing by mitosis. Mitosis produces two to eight haploid cells called zoospores. Many zoospores break out of the parent cell and grow to become mature haploid cells.
Sexual reproduction among unicellular protists
During environmental stress certain protists reproduce sexually - haploid cells divide by mitosis producing haploid gametes - a pair of gametes fuse to form a …show more content…
pair - this pair sheds their cell wall and fuse into a diploid zygote o zygospore (thick protective wall) can withstand unfavorable conditions
Sexual reproduction among multicellular protists
There are a variety of ways in which protists reproduce sexually: 1. alternation of generations – two distinct multicellular phases a. sporophyte generation – diploid (spore producing phase) i. reproductive cells called sporangia produce haploid spores by meiosis b. gametophyte generation – haploid (gamete producing phase) i. produce gametophyte haploid gametes that fuse divide through mitosis 2. conjugation- the temporary union of two protists to exchange nuclear material a. two filaments align side by side b. cell walls form a bridge between the cells c. the nucleus of one then passes through the tube into the other cell d. the two nuclei form a resting spore e. producing an new haploid
22-2: Protists Diversity
Protists Can Move by Using Cytoplasmic Extension
Amoebas and forams are unicellular heterotrophs that have a unique form of movement.
Ameobas – phylum Rhizopoda - move by using flexible, cytoplasmic extensions – pseudopodia - extremely flexible, no cell wall - pseudopodia surrounds and engulfs food particle - live in freshwater and salt water - reproduce by binary fission – dividing into two new cells - most free-living, some parasitic
Forams – phylum Foraminifera - marine protists - live in sand or attach themselves to other organisms or rocks - porous shells – tests - have many chambers arranged in a spiral shape - cytoplasm extends through the pores in the test to aid in swimming and catching prey - have symbiotic relationship with algae - dead accumulate on ocean floors to form limestone deposits
Diatoms Have Double Shells
Diatoms – phylum Bacillariophyta - photosynthetic - unicellular protists - unique double shells made of silica - shells like small boxed with lids - abundant in oceans and lakes - important producers - have two types of symmetry o radial – like a wheel o bilateral – mirror image
- shells form diatomaceous earth used as an abrasive or in paint used on roads - natural control for pests - move by secreting chemicals through and gliding across a surface - diploid and usually reproduces asexually – two halves of the shell separate and regenerates o tend to get smaller and smaller
Many Algae Are Multicellular
Some are unicellular, while most are multicellular. Algae are distinguished by the type of photosynthetic pigment they contain and by their cell or body shape.
Green algae – phylum Chlorophyta - freshwater unicellular - some are large, multicellular marine organisms - major part of microscopic marine plankton - live in damp soil or thrive within the cells of other organisms – symbiosis - contain the same pigments found in chloroplasts of plants - have both sexual and asexual reproductive stages
Red algae – phylum Rhodophyta - multicellular - found in warm ocean water - red pigments can absorb the light that penetrates deep waters - some have calcium carbonate in their cell walls - others are used to make agar and carrageenan – ice cream - complex life cycle, usually involving alternation of generations
Brown algae – phylum Phaeophyta - multicellular - found in marine environments - larger know as kelp – grow along coasts and provide food and shelter for many different organisms - among the largest organisms on Earth
Some Protists Move with Flagella
Flagellates are protists that move using flagella. There are three major groups: 1. Dinoflagellates – phylum Dinoflagellata - unicellular phototrophs - most have two flagella - few are found in freshwater - most are marine and make up part of the plankton - have a protective coat made of cellulose and silica – unusual shapes - flagella in two grooves – spin through the water like a top - few produce toxins – red tides - reproduce asexually by mitosis
2. Zoogastigotes – phylum Zoomastigina - unicellular heterotrophs - have at least one flagella, some have thousands - most reproduce only asexually - some produce gametes and reproduce sexually - symbiosis – Trichonympha live in the guts of termites providing an enzyme that digests wood - trypanosomes causes diseases in humans and animals – African sleeping sickness
3. Eugleniods – phylum Euglenophyta - freshwater protists with two flagella - one-third of the 1,000 species of hove chloroplasts – photosynthetic - others lack chloroplast and ingest their food – heterotrophic - Euglena – pellicle = protein scaffold - can change shape - eyespot = light-sensitive organ helps orient the movement toward light - reproduce by mitosis
Ciliates Are Complex Protists That Use Cilia to Swim
Ciliates are the most complex and unusual of the protists.
Ciliates – phylum Ciliophora - have large numbers of cilia = tightly packed rows of short flagella used for movement - complex unicellular heterotrophs - body walls are tough but flexible – can squeeze through or around many obstacles - form vacuoles for ingesting nutrients and regulating their water balance - most have two nuclei o micronuclei = contains normal chromosomes that divide by mitosis o macronuclei – contains small pieces of DNA derived from micronuclei used in routine cellular functions - reproduces by mitosis – splitting in half - can engage in sexual reproduction by conjugation
Protists Molds Are Not Fungi
Protistan molds are heterotrophs with some mobility. They have cell walls made of carbohydrates.
Cellular slime molds – phylum Acrasiomycota - move through soil and digest bacteria - during environmental stress they gather together forming multicellular colonies called slugs - slugs develop a base, a stalk and a swollen tip that develop spores - each spore becomes a new organism and begins to
feed
Plasmodial slime molds – phylum Myxomycota - stream along a mass of cytoplasm that looks like an oozing slime – plasmodium - as they move, they engulf bacteria and other organic material - contain many nuclei but are not separated by a cell wall - when it begins to starve or dry out it divides in order to survive
Other molds – phylum Oomycetes - water molds, white rusts and down mildews - often grow on dead algae and dead animals in freshwater - either parasites or feed on dead organic matter - have two flagella – one pointed forward the other pointed backward - many are plant pathogens – blight in potatoes
Some Protists Form Resistant Stages
Parasitic protists that form spores during reproductive cycle are called sporozoans.
Sporozoans - phylum Apicomplexa - 4,500 species - nonmotile, unicellular - parasites that cause many diseases – Malaria - have complex life cycles that involve both asexual and sexual reproduction - infect animals and are transmitted from host to host - transmitted by another host by blood-feeding insects – mosquitoes, black flies - can be transmitted in the feces of an infected animal - can be transmitted through predation
22-3: Protists and Health
How Do Protists Affect Humanity
One of the greatest effects protists have on humans is that they cause disease. See table on page 490.
Beneficial protists
There are many commensal protists that live in the digestive tracts of humans and in the digestive tracts of the animals that humans eat. Protists are the single largest group of photosynthesizers on the planet. Many protists are detritivores.
Malaria Is Caused by Several Species of Plasmodium
Malaria is one of the most deadly diseases in humans.
Malaria life cycle
Malaria is caused by several species of Plasmodium and is spread by the bite of certain mosquitoes. See page 491 for the life cycle.
sporozoite = the infective stage of Plasmodium
merozoite = second stage of Plasmodium, in which the protist divides rapidly in RBC’s and produces many more merozoites
Treating and preventing malaria
Quinine was discovered to be a remedy for malaria. Reducing the mosquito population can also control malaria.