Plant Reproduction: Anthophyta and Morphogenesis

Plant Reproduction (Anthophyta ONLY)

• Angiosperms' major evolutionary adaptation is the development of flowers and fruit

Phase Change

• Developmental changes lead to reproductive maturity, also known as flowering
• Flowering can be triggered by external or hormonal cues
• Light, temperature and hormones are examples of these cues
• Short-day plants flower in shorter days and longer nights (e.g., Christmas Cactus, Poinsettias)
• Long-day plants flower in longer days and shorter nights (e.g., Clover)
• Temperature changes such as stratification and vernalization play a role
• Plants can be autonomous and not rely on environmental cues
• Changes involved in flowering can be subtle or obvious (e.g., oak leaves in winter, aerial roots on ivy)

Morphogenesis

• Floral structures are modified leaves and are arranged in whorls
• Calyx are the sepals
• Corolla are the petals
• Androecium are the stamens, which consist of filament and anther
• Gynoecium are the carpels, which consist of ovule, ovary, style and stigma
• Complete or incomplete flowers

Floral Evolution

• Radial symmetry involves grouped or fused parts and can be lost or reduced to increase pollination efforts
• Bilateral symmetry involves grouped or paired structures to increase pollination effects

Gamete Production

• Alternation of generations results in diploid sporophyte to haploid gametophyte
• Male gametophyte produces microspores, also known pollen grains
• Female gametophyte produces megaspores, also known as the embryo sac

Pollination

• Pollination refers to pollen transfer to the stigma
• Self-pollination occurs within the same flower
• Cross-pollination (outcrossing) occurs between different plants
• Pollination can be dioecious, monoecious, and dichogamous

Wind Pollination

• Wind-pollinated flowers have corollas that are absent or greatly reduced and are monoecious

Pollinators

• Bees and moths and butterflies
• Birds and others like bats and monkeys

Double Fertilization

• This process leads to the formation of the embryo and (3n) endosperm
• Germination of the pollen grain develops a pollen tube
• Generative cell divides to form 2 sperm cells
• One sperm fertilizes the egg, and the other fertilizes the polar nuclei to form triploid endosperm

Embryonic Development

• The suspensor and embryo are part of embryonic development
• Development of protoderm, ground meristem, and procambium occurs in the globular stage
• Cotyledons are derived from embryonic tissues
• Seeds can undergo dormancy and dispersal

Germination

• Water and oxygen penetrate the seed coat
• Radicle emerges

Plant Life Spans

• Perennial plants can be deciduous or evergreen
• Annual plants and Biennial plants

Protists: General Biology

• Highly variable cell surfaces such as in Plasma membrane or through extracellular material
• Cysts facilitate dormancy and disease transmission
• Locomotion is achieved through flagella, cilia, and pseudopodia that can be Lopopods, Filopods, or Axopods
• Feeding strategies include autotrophs, heterotrophs, and mixotrophs
• Asexual reproduction involves mitosis, budding, and schizogony
• Sexual reproduction occurs obligately under stress involving meiosis with genetic recombination

Multicellularity

• Cells, colonies, and multicellularity can form
• Protists are the most diverse eukaryote groups and are present in 5 supergroups

Excavata

• Diplomonads are unicellular and have flagella and 2 haploid nuclei (example is Giardia)
• Euglenozoa have flagella and a flexible pellicle and reproduce asexually via mitosis
• 1/3 of Euglenozoa species have chloroplasts (autotrophic), 2/3 are heterotrophic, and can be mixotrophic
• Euglenozoa: Kinetoplastids are parasitic trypanosomes that cause human diseases
• African sleeping sickness, vector is Tsetse fly and Trypanosomiasis
• Chagas disease is transmitted by the Triatomine bug, and Leishmaniasis

SAR

• SAR includes Stramenopila, Alveolata, and Rhizaria
• Stramenopila includes brown algae and diatoms with extracellular matrix made of silica
• Oomycetes include the Irish potato famine
• Alveolata are characterized by flattened vesicles called alveoli
• Dinoflagellates are unicellular and flagellated and some are luminescent (Karenia brevis)
• Apicomplexa are spore-forming parasites such Plasmodium that causes malaria with a complex life cycle and stages
• Ciliates have rows of cilia arranged in a spiral with a pellicle and 2 types of nuclei (Paramecium)
• Rhizaria utilize pseudopods
• Radiolaria have silica exoskeletons with needle-like pseudopods (Foraminifera)

Cercozoa

• Cercozoa are heterotrophic marine organisms that make up the Cliffs of Dover (limestone) and are found in soil with flagella or pseudopods

Archaeplastida

• Archaeplastida inclues Rhodophyta, Chlorophyta, Charophyta and Land plants

Amoebozoa

• Amoebozoa use pseudopods for locomotion and feeding, such as Naegleria fowleri or slime molds

Opisthokonta

• Opisthokonta includes animals, fungi, and choanoflagellates
• Choanoflagellates have a contractile collar and resemble the closest animal relatives