Eukaryotic Cells, Protists, and Plant Evolution: Key Traits and Processes

What are the key traits of eukaryotic cells?

Flexible cell membrane, complex cytoskeleton, nuclear membrane, and organelles.

What is the function of the flexible cell membrane in eukaryotic cells?

Allows cells to change shape, move in new ways, and obtain substances from their surroundings.

What processes allow eukaryotic cells to take in substances through their membrane?

Endocytosis (fluids) and phagocytosis (particles).

What is the role of the nuclear membrane in eukaryotic cells?

It surrounds DNA and separates transcription and translation processes.

What are digestive vacuoles in eukaryotic cells?

Structures that take in food and merge with lysosomes to break it down.

What are the five groups of protists?

Excavates, Alveolates, Stramenopiles, Rhizarians, and Amoebozoans.

What distinguishes Excavates from other protist groups?

Some lack or have modified mitochondria and are thought to be base protists.

What are the two theories regarding the origin of mitochondria in Excavates?

Late origin (acquired later) and early origin (lost after divergence).

What are the main groups within Excavates?

Diplomonads, Parabasalids, Kinetoplastids, Heteroloboseans, and Euglenids.

What is a characteristic of Euglenids?

They have flagella for movement and can switch between photosynthesis and heterotrophy.

What are the main groups within Alveolates?

Dinoflagellates, Ciliates, and Apicomplexans.

What is a defining feature of Stramenopiles?

They possess two flagella.

What are diatoms known for?

Being photosynthetic unicells with silica in their cell membranes.

What is the role of Rhizarians?

Aquatic organisms with pseudopodia used for movement and food capture.

What are Amoebozoans characterized by?

Heterotrophs that engulf food using pseudopods.

What is the typical asexual reproduction method in unicellular eukaryotes?

Binary fission, where the cell copies its DNA and splits into two identical daughter cells.

What is the difference between haploid and diploid cells?

Haploid cells have one chromosome, while diploid cells have two.

What occurs during meiosis in sexual reproduction?

A diploid cell divides to produce four haploid cells.

What is fertilization in the context of eukaryotic reproduction?

The fusion of two haploid gametes to form a diploid zygote.

What is a diplontic life cycle?

A life cycle where the adult is diploid and produces gametes that fuse to form a diploid zygote.

What is a haplonic life cycle?

A life cycle where the adult is haploid and undergoes mitosis to produce gametes.

What is the typical protist haplonic life cycle?

Starts haploid, undergoes vegetative replication, then forms gametes under stress, fusing to create a zygote.

What is a mating type locus?

A gene that determines the mating type of a haploid organism.

What are the benefits of sexual reproduction?

It introduces new combinations of alleles, helping to phase out harmful mutations.

What are the two types of gametes in eukaryotes?

Positive (gsp) and negative (gsm) gametes.

What is the role of the zygote in eukaryotic reproduction?

The zygote has both + and - gametes, enabling transcription of new genes and meiosis.

What significant evolutionary event occurred during the Cambrian Period?

The Cambrian explosion, marked by a great diversity of life forms.

What major extinction event occurred during the Ordovician-Silurian period?

The first major extinction that wiped out most sea life due to dropping water levels.

What characterized the Devonian period in terms of evolution?

The emergence of fish with jaws and increased terrestrial diversity.

What significant geological event occurred during the Carboniferous period?

The formation of Pangea and the rise of large reptiles.

What type of organisms first appeared during the Jurassic period?

The first known flowering plants.

What was the impact of the Cretaceous extinction event?

An asteroid wiped out the dinosaurs, leading to the Tertiary period.

What are the five requirements for multicellularity?

Cells must stick together, specialize, allocate resources, inhibit growth/reproduction, and have programmed cell death.

What advantages do multicellular photosynthetic organisms have?

They possess flat leaves for sunlight, tubular stems, and roots for water absorption.

How do multicellular absorptive organisms capture food?

They release spores and hyphae to digest and absorb nutrients.

What is the significance of Chlamydomonas in the evolution of multicellularity?

Chlamydomonas is a green algal protist related to Volvox, which is multicellular.

What are the stages of multicellularity from unicellular to complex forms?

Unicellular, colonial, filamentous, and parenchymatous.

What are the benefits of multicellularity?

Increased size, power, cell specialization, and efficiency.

What are the challenges of multicellularity regarding reproduction?

Organisms must decide between asexual reproduction or sexual reproduction to manage mutations.

What is the role of meiosis in multicellular organisms?

Meiosis produces haploid gametes that can fertilize into diploid zygotes.

What adaptations did plants develop to transition from aquatic to land environments?

Support structures, methods for gamete transfer through air, and nutrient transport systems.

Why did plants move to land approximately 470 million years ago?

For direct sunlight, increased oxygen, more nutrients, and lack of herbivore predation.

What challenges did early land plants face?

Lack of water support, difficulty in gamete transfer, nutrient transport, and gravity resistance.

What likely helped algae transition to land?

Fungi, which release digestive enzymes to break down rock and provide nutrients.

What are the four main groups of land plants?

Bryophytes (moss), Pteridophytes (ferns), Gymnosperms (trees), Angiosperms (flowering plants).

What is a key adaptation of land plants to protect their embryos?

Enclosed embryos within gametophytes.

What is the primary difference between haplontic and haplo-diplontic life cycles?

Haplontic organisms, like algae, spend most of their life in the haploid state, while haplo-diplontic organisms, like plants, have both haploid and diploid generations.

What is the role of xylem in vascular plants?

Xylem is responsible for the movement of water and ions.

What are the two types of spores produced by gymnosperms?

Megaspores (which develop into eggs) and microspores (which develop into sperm).

What evolutionary advancement do angiosperms have over gymnosperms?

Angiosperms have flowers that attract animals for pollination.

What are the three primary parts of a plant?

Root, stem, and leaf.

What is the function of meristem cells in plants?

Meristem cells can differentiate into any part of the plant as needed, facilitating growth.

What is secondary growth in plants?

Growth that increases the diameter of the plant, caused by cell division in vascular cambium and cork cambium.

What are the main organs of a flower?

Sepals, petals, stamens, and carpels.

What is the function of Hox genes in animals?

Hox genes are master regulators that specify the development of body plans and structures.

What are the six major groups of animals?

Porifera (sponges), Ctenophores (comb jellies), Placozoa, Cnidaria, Protostomes, and Deuterostomes.

What is the significance of gastrulation in animal development?

Gastrulation transforms a simple cluster of cells into a structured body layout, forming layers that develop into different tissues.

What are the three germ layers formed during gastrulation?

Ectoderm (outer layer), mesoderm (middle layer), and endoderm (inner layer).

What distinguishes protostomes from deuterostomes?

In protostomes, the mouth forms first; in deuterostomes, the mouth forms second (humans are deuterostomes).

What is the role of stomates in plants?

Stomates control water and air movement in plant tissues.

What is vegetative growth in plants?

Growth that involves stem and leaf production through mitosis, increasing cell numbers.

What is the function of phloem in vascular plants?

Phloem is responsible for the movement of sugars throughout the plant.

What is the difference between primary and secondary growth in plants?

Primary growth increases the length of the plant, while secondary growth increases its diameter.

What is the function of the carpel in flowers?

The carpel is the female organ of the flower, containing the ovule which develops into seeds.

What type of symmetry do humans exhibit?

Bilateral symmetry.

What is the significance of the extracellular matrix in animals?

It helps cells stick together and provides structural support.

What is the role of cork in woody plants?

Cork protects the inner layers of the tree.

What is the primary function of the root in plants?

To anchor the plant and absorb water and nutrients from the soil.

What is a coelom?

A body cavity with internal organs.

What are the three variations of body cavities?

Acoelomate (no coelom), Pseudocoelomate (one layer of mesoderm), Coelomate (two layers of mesoderm, as in humans).

What is segmentation in animals?

The division of the body into segments that can be the same or different, aiding in diversification.

What role do appendages play in animal evolution?

They enable specialization and movement on segments.

What is the function of the nervous system in animals?

To gather information and coordinate movement.

What is an echinoderm?

A member of a group of marine animals that are characterized by a hard, spiny covering.

What is a notochord?

A flexible rod-like structure that serves as a backbone in chordates.

What defines a craniate?

An animal that has a head.

What is the vertebral column?

A structure that sits on top of the notochord, forming the backbone.

What is the significance of osteichthyes?

They are bony fish that evolved from earlier forms with mineralized skeletons.

What are tetrapods?

Four-limbed vertebrates that evolved from lobed-finned fish.

What is the purpose of amniotic eggs?

To keep water in and facilitate gas exchange for developing embryos.

What adaptations were necessary for animals to transition to land?

Mobility for mating, protection of vulnerable stages, strong skeletons, and systems for conserving water and nutrient transport.

What significant event led to most animal diversity?

The Cambrian explosion.

Which groups of animals evolved before the Cambrian explosion?

Annelids, chordates, molluscs, and cnidarians.

What evidence supports the existence of ancestral sponges?

Pre-Cambrian fossil records show no specialized cells.

What triggered the Cambrian explosion?

The evolution of Hox genes, increased oxygen levels, the appearance of predators, and favorable ocean conditions.

How did increased oxygen levels affect animal evolution?

It supported larger, more active animals.

What evolutionary changes occurred due to the appearance of the first predators?

The evolution of shells, armor, and enhanced movement.

What environmental conditions contributed to the Cambrian explosion?

Warmer, nutrient-rich oceans and shallow seas provided better habitats for life.

What is the role of the retina in eye development?

The retina is necessary for lens formation; it signals the lens to develop.

What happens when the eye cup is removed from a developing embryo?

Both the retina and lens fail to form, indicating the eye cup's necessity.

What are homeotic genes?

Genes that act as transcription factors and regulate the development of body parts in embryos.

What are the three basal groups of metazoans?

Sponges, ctenophores, and cnidarians.

What type of symmetry do cnidarians exhibit?

Radial symmetry.

What are the key features of sponges?

Multicellular, diploblasts with simple diffusion for gas exchange and a lack of specialized tissues.

What are the main cell types found in sponges?

Choanocytes, porocytes, and amoebocytes.

What is the feeding mechanism of cnidarians?

They capture prey with cnidocytes and can directly absorb nutrients.

What distinguishes ctenophores from cnidarians?

Ctenophores have two openings (mouth and anus) and exhibit rotational symmetry.

What are the two major groups of protostomes?

Lophotrochozoans and ecdysozoans.

What are the characteristics of lophotrochozoans?

They include annelids and mollusks, characterized by cilia for feeding.

What is a key feature of annelids?

They are segmented animals with a closed circulatory system.