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Questions and Answers
Which of the following are differences between plants and animals? (Select all that apply)
Plants generally respire by taking in ______ and releasing ______.
CO2, O2
What is plasmodesmata?
Channels that connect living parts of plant cells.
Eukaryotic cells have a membrane-bound nucleus.
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What evidence supports the endosymbiosis theory?
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Which of the following is a characteristic of Laminaria (Brown Algae)?
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What pigment gives Red Algae its red color?
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What are the key traits that indicate plants evolved from green algae?
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Bryophytes are ______ plants.
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What type of nutrition do plants have?
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Plants can move around freely like animals.
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What structure connects the cytoplasm of adjacent plant cells?
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Which of the following is a feature of eukaryotic cells?
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What type of algae is Laminaria?
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How many species of Polysiphonia are there?
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The pigment that gives red algae its color is called ______.
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Bryophytes are considered vascular plants.
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What do Chlamydomonas primarily live in?
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Plants evolved from ______.
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Match the following types of algae with their characteristics:
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Study Notes
Plants vs Animals
- Plants are generally immobile, whereas animals can move freely.
- Plants are autotrophs, meaning they produce their own food through photosynthesis. Animals are heterotrophs, meaning they obtain food from other organisms.
- Plants intake CO2 and release O2 during respiration, while animals intake O2 and release CO2.
- Plants possess sophisticated systems to respond to stimuli like light, gravity, temperature, and touch. Animals have a nervous system for this purpose.
- Plant growth is continuous throughout life and restricted to specific meristematic regions. Animal growth is not restricted to specific regions and is definite.
- Both plants and animals have basic cell features. However, plants have additional structures like chloroplasts, cell walls, vacuoles, and plasmodesmata.
Plant Cell Features
- Plasmodesmata: Channels connecting living parts of plant cells, enabling cytoplasm to connect and form a living continuum. Water and small solutes can pass freely through this pathway (symplastic route).
- Symplast: The continuous network of cytosol connected by plasmodesmata.
- Apoplast: The continuous network of cell walls and extracellular spaces.
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Basic features of all cells:
- Bounded by a plasma membrane
- Cytosol with subcellular components
- Chromosomes
- Ribosomes
Prokaryotic vs. Eukaryotic Cells
- Location of DNA: In prokaryotes, DNA is located in the cytoplasm. In eukaryotes, DNA is located in the nucleus.
- Membrane-bound organelles: Eukaryotes have membrane-bound organelles like mitochondria, nucleus, endoplasmic reticulum, and Golgi apparatus, which are absent in prokaryotes.
Endosymbiosis Theory
- An ancestral prokaryote folded its plasma membrane inwards, creating the nucleus and endoplasmic reticulum.
- This ancestral eukaryote engulfed an aerobic bacterium, which evolved into the mitochondrion.
- This heterotrophic eukaryote then engulfed a photosynthetic bacterium, leading to the development of chloroplasts and ancestral photosynthetic eukaryotes.
Evidence for Endosymbiosis
- Organelles like mitochondria and chloroplasts have two membranes. One is attributed to the original prokaryotic cell, and the other is derived from the host cell's plasma membrane.
- Inner membranes of these organelles contain enzymes and transport systems similar to those found in the plasma membranes of living bacteria.
- Mitochondria and chloroplasts are autonomous; capable of transcription and translation, possessing their own circular DNA.
Supergroups of Eukaryotes
- Excavates
- SAR (Stramenopiles, Alveolates, Rhizaria)
- Brown algae
- Archaeplastida
- Red algae
- Green algae
- Plants
- Unikonta
Brown Algae
- Almost entirely marine, found in cooler regions on rocky shores
- Approximately 1500 species
- Exhibit alternation of heteromorphic generations, meaning the sporophyte and gametophyte have distinct morphologies.
Red Algae
- Found in tropical and warm waters
- Around 6000 species
- Exhibit a unique life cycle with 3 multicellular stages.
- Contains the pigment phycoerythrin, giving it its red color.
- Lacks flagellated sperm; relies on water to transport sperm to egg cells.
Green Algae
- Aquatic
- About 7000 species
- Unicellular and used as model organisms.
- Reproduce both sexually and asexually. Sexual reproduction is triggered by stress, increasing species survival chances.
Bryophytes
- Plants evolved from green algae, evidenced by shared key traits:
- Multicellular, eukaryotic, photosynthetic autotrophs
- Cell walls composed of cellulose
- Chloroplasts containing chlorophylls a & b.
- Flagellated sperm
- Pigments like β-carotene and xanthophylls
- Enzyme glycolate oxidase for photorespiration.
- Closest relatives of plants are a group of green algae called charophytes, sharing distinctive traits:
- Rings of cellulose-synthesizing proteins
- Flagellated sperm
- Phragmoplast during cell division
Plant and Animal Differences
- Plants generally cannot move while animals can move freely.
- Plants are autotrophs meaning they make their own food, while animals are heterotrophs meaning they eat other organisms.
- Plants take in CO2 and release O2 during respiration, while animals take in O2 and release CO2.
- Plants have sophisticated systems to respond to light, gravity, temperature, and touch, while animals have a nervous system.
- Plant growth is restricted to certain meristematic tissue regions and is continuous throughout life, animal growth is not restricted and is definite.
- Plants have chloroplasts, cell walls, vacuoles, and plasmodesmata in addition to basic cell features, animals only have basic cell features.
Plasmodesmata, Symplast, and Apoplast
- Plasmodesmata are channels connecting the living parts of plant cells.
- These channels allow the cytoplasm of adjacent cells to be connected, forming a symplast or living continuum.
- Water and small solutes can move freely through the symplast.
- The apoplast is the space outside the plasma membrane, including cell walls and extracellular spaces.
Cellular Structure
- All cells are bounded by a plasma membrane.
- Cells contain cytosol, subcellular components, chromosomes, and ribosomes.
- Prokaryotic cells have DNA located in the cytoplasm, while eukaryotic cells have DNA located in the nucleus.
- Eukaryotic cells have membrane-bound organelles including mitochondria, nucleus, ER, and Golgi apparatus, while prokaryotic cells do not.
Endosymbiosis Theory
- The endosymbiosis theory explains the origin of eukaryotic cells.
- An ancestral prokaryote's plasma membrane folded inwards, creating the nucleus and ER.
- This ancestral prokaryote then engulfed an aerobic bacterium, which became the mitochondrion, creating the ancestral eukaryote (heterotroph).
- The ancestral heterotroph then engulfed a photosynthetic bacterium, which became the chloroplast, creating the ancestral photosynthetic eukaryote.
Evidence for Endosymbiosis
- Organelles are bounded by two membranes, indicating an engulfment event.
- The inner membrane of organelles contains enzymes and transport systems homologous to those found in bacteria.
- Organelles are autonomous, capable of transcription and translation.
- Organelles have circular DNA, similar to bacterial DNA.
Algae
- Algae are classified into four supergroups: Excavate, SAR, Archaeplastida, and Unikonta.
- Archaeplastida includes red algae, green algae, and plants.
Laminaria (Brown Algae)
- Brown algae are almost entirely marine and thrive in cooler regions of the world.
- They exhibit alternation of heteromorphic generations: sporophyte and gametophyte are morphologically different.
- The life cycle starts with male gametophytes releasing sperm and female gametophytes producing eggs.
- Fertilization creates a diploid zygote, which develops into a sporophyte.
- The sporophyte produces zoospores (motile spores) through meiosis.
- Zoospores develop into independent male and female gametophytes through mitosis.
Polysiphonia (Red Algae)
- Red algae are found in tropical and warm waters.
- They have a unique three-phase multicellular life cycle, exhibiting alternation of generations.
- Phycoerythrin is a pigment that gives red algae their color.
- Red algae lack flagellated sperm and rely on water to carry sperm to the egg.
- The life cycle starts with fertilization creating a diploid zygote.
- The zygote develops into a carpogonium, which produces diploid carpospores.
- Carpospores germinate and develop into a sporophyte.
- The sporophyte produces sporangium, which produces haploid spores through meiosis.
- Germinating spores develop into gametophytes.
Chlamydomonas (Green Algae)
- Chlamydomonas are aquatic and are often used as a model organism.
- They can reproduce both sexually and non-sexually.
- Sexual reproduction is favored when there is stress, increasing survival chances.
Ulva (Green Algae)
- Ulva is found in water, commonly along temperate seashores.
- It exhibits alternation of isomorphic generations, where gametophyte and sporophyte are morphologically similar.
Bryophytes
- Bryophytes are non-vascular plants, including mosses, liverworts, and hornworts.
- They are thought to have evolved from green algae.
- Key traits of plants are also found in some algae.
Bryophyte Traits
- Multicellular, eukaryotic, photosynthetic autotroph.
- Cell walls composed of cellulose.
- Chloroplasts containing chlorophylls a and b.
- Flagellated sperm.
- Pigments β-carotene and xanthophylls.
- Enzyme glycolate oxidase for photorespiration.
Charophytes
- Charophytes are a group of green algae that are the closest relatives of plants.
- They share several distinctive traits with plants, including rings of cellulose-synthesizing proteins and flagellated sperm cells.
- Charophytes are thought to be the ancestors of plants and play a crucial role in understanding plant evolution.
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Description
Test your knowledge on the fundamental differences between plants and animals. Explore their unique characteristics, growth patterns, and cellular structures. This quiz covers essential biological concepts related to autotrophs and heterotrophs.
