Reproduction Flashcards
What is natural selection?
- Selects for genes that enable an organism to survive and reproduce
- Driving force of evolution
What is asexual reproduction?
-Genetically identical cells are produced from single parent cell through mitosis
What are the types of asexual reproduction?
- Binary fission: division of one cell into two equal or almost equal parts (daughter cells)
- Budding: adult cell/organism grows smaller daughter cell or organism
- Vegetative reproduction: new individuals are created from parts of adults
- Fragmentation: in simple animals
- Parthenogenesis (in animals) or Apomixis (in plants) is having offspring from an unfertilized egg
Describe sexual reproduction?
-Reproduction that involves the combination of genetic info. from two parent individuals (only in eukaryotes)
What are the pros and cons of sexual reproduction?
Pros: genes recombine to form entirely new genome
Cons: must find mate and undergo mating
What are the types of sexual reproduction?
- Ciliates undergo conjugation (genes transferred through micronucleus, micronuclei fuse together to form new genome)
- Fertilization: where two cells fuse to one, most multicellular organisms produce haploid gametes (sperm and egg produce diploid zygote
Describe dioecious and monoecious?
Dioecious: organism that produces one type of gamete, male/female
Monoecious: produces both types of gametes, hermaphroditic, may or may not self fertilize
What are spores?
- Haploid reproductive cell that gives rise to a gametophyte
- May form from sexual or asexual processes (always haploid)
Describe diplontic and haplodiplontic life cycles?
Diplontic: only diploid stage is multicellular, haploid stage is one gamete cell
Haploidiplontic: multicellular diploid stage (sporophyte), and multicellular haploid stage (gametophyte)
Describe chlorophytes and charophytes?
- Haplodiplontic life cycles
- Gametophyte and sporophyte appear identical
- +/- gametes
Describe brown algae?
- Haplodiplontic life cycles
- Gametophyte is reduced, sporophyte is dominant
- Egg and sperm
Describe Bryophytes?
-Haplodiplontic
-Gametophyte dominant: Archegonia (female), Antheridia (male)
-After fertilization:
Archegonia grows a sporophyte stalk
Sporophyte is nonphotosynthetic
Sporophyte produces spores
-Need to be in moist environment
Describe Pteridophytes?
-Haplodiplontic
-Sporophyte dominant
Produces sori on back of fronds
Small gametophyte with antheridia and archegonia
Sperm fertilizes egg and sporophyte grows from archegonium
Describe seed plants?
-Haplodiplontic
-Seed plants produce 2 kinds of gametophytes
Male gametophytes: microgametophyte (pollen grains, dispersed by wind or pollinator)
Female gametophytes: megagametophyte (develop within an ovule, enclosed within diploid sporophyte tissue)
What is the difference between pollen and spores?
- Pollen: used for fertilization (sperm)
- Spores: gown into gametophyte generation
Describe gymnosperms?
- Sporophyte produces male and female cones
- Pollen grains develop into male cones by meiosis
- Female cones are larger with woody scales
- When scales of female cones are open, pollen grains drift between them
- Pollen tube emerges from pollen grain which digests its way to embryo sac to deliver sperm
What are angiosperms?
Possess flowers and fruits
Describe flower structure?
- A complete flower has four whorls
- An incomplete flower lacks one or more whorl
- Calyx: consists of sepals
- Corolla: consists of petals
- Androecium: collective term for stamens, a stamen consists of a filament and anther
- Gynoecium: collective term for carpels, carpels consist of an ovule, ovary, style, and stigma
What is a microgametophyte?
- Four microspores form through meiosis and become pollen grains
- Each consist of a tube cell, generative cell will later divide to form two sperm cells
What is a megagametophyte?
- Female gametophyte has 8 haploid nuclei
- 2 become polar nuclei
Describe pollination?
- Process which pollen is placed on stigma
- Self pollination: pollen from flowers anther pollinates stigma of same flower
- Cross pollination: pollen from anther of one flower pollinates another flowers stigma (more common)
What are some pollinators?
- Bees: most common insect pollinators
- Butterflies: prefer flowers with flat “landing platforms”
- Birds: like red flowers
Describe fertilization?
-Angiosperms undergo a unique process called double fertilization
Tube cell forms a pollen tube
Generative cell divides to form 2 sperm cells
-One sperm cell fuses with egg cell to form diploid zygote
-Other sperm cell nucleus fuses with the two polar nuclei to form the triploid endosperm
How do fungi fertilize?
- Merge hyphae cells from two individuals
- Nuclei fusion in a process called karyogamy, forming a diploid zygote
- Sometimes forms a dikaryotic cell before karyogamy
How do Basidiomycota fertilize?
- Spore germination leads to production of haploid mycelium
- Mycelium may fuse to result in fertilization (now dikaryotic)
- Basidiocarps (mushrooms) form from secondary mycelium
- Dikaryotic basidiocarp has hundreds of basidia in each gill
Describe animal fertilization?
-Diplontic, most reproduce sexually
Describe internal and external fertilization?
- Internal: sperm introduced into female reproductive tract
- External: eggs and sperm are released into water where union of free gametes occur
Describe the three strategies of development in internal fertilization?
- Oviparity: Fertilized eggs deposited outside of body to complete their development
- Ovoviviparity: Fertilized egg is kept in mother to complete development and young obtain food from egg yolk
- Vivipartiy: Young develop within mother and obtain nourishment from her blood
Describe fertilization in aquatic vertebrates?
- Cartilaginous fish: internal fertilization
- Bony fish and most amphibians: external fertilization
What are amniotes?
- Animals with amniotic egg
- Amniotic egg has four membranes
- It’s water tight
- It results from internal fertilization
Describe the parts of an egg?
- Amnion: fluid, maintains chemical consistency and temperature
- Yolk Sac: 2nd membrane, encloses the yolk of eggs full of nutrients, proteins, fats
- Allantois: 3rd membrane: stores metabolic wastes, acts as respiratory surface exchanging gases
- Chorion: 4th and outermost protective membrane fused to allantois, gas exhange
Describe reproduction in reptiles and birds?
-Most are oviparous, lay amniotic egg, birds incubate egg to keep it warm
Describe mammal reproduction?
- Female reproductive cycles involve periodic release of mature egg (ovulation)
- Most have estrous cycles (females are receptive to males only around ovulation, estrus)
- Primates have menstrual cycles (shed inner lining of uterus, menstruation)
Describe the different mammals and how they reproduce?
- Monotremes: are oviparous (lay amniotic eggs)
- Marsupials: ovoviviparous, give birth to incompletely developed fetuses which mature in mothers pouch
- Placentais: are viviparous, retain young in uterus for long periods of development
What is a placenta?
- Derived from amniotic egg and the lining of the mothers oviduct
- Embryo is plugged into mother and exchanges nutrients and waste with her
- Brings fetal and maternal blood into close contact
