week 10 - reproduction

Describe the advantages and disadvantages of asexual reproduction?

• Advantages - doesnt require mate, therefore increases rapidly

• Disadvantages - offspring’s are identical clones, meaning reduced genetic diversity

• Low capacity to adapt

What are the main methods of asexual reproduction?

• Binary fission

• Budding

• Fragmentation

• Parthenogenesis

Describe binary fission?

• Single parent that divides into two genetically identical daughter cells

• Replicates genetic material via mitosis

• Commonly happens with bacteria and protist

Describe budding?

• Instead of dividing, it outgrows from the parent

• New individual develops from the body of parent

• Repeated miotic cell divisions

• Once fully developed, might detach e.g hyrda

Describe fragmentation?

• Organism breaks off and forms offspring

• Means organism can survive catastrophic breaks

• Can happen due to predation or stress

• Happens to sponges, sea stars

Describe parthenogenisis?

• Offspring developed from unfertilised eggs, no need for sperm

• Happens in some fish and reptiles

• Some species mix with sexual reproduction, allowing for rapid reproduction and genetic diversity

Describe sexual reproduction in animals?

• Involves gametes from male and female to produce zygote

• Allows for high genetic diversity, allowing for adaption

Describe external fertilisation?

• Sperm and egg released into the environment and fuse outside the body

• Happens in aquatic habitats where water helps spears travel to eggs

• Allows to produce lots of gametes and offspring

• Fertilisation is low due to exposed predation and environmental hazards

Describe internal fertilisation?

• Sperm is directly transferred into female reproductive tract

• Increased fertilisation rate

• Requires greater energy, specialised structures

• Higher offspring survival

Describe monoecious and dioecious?

• Monoecious - organism that possesses both male and female reproductive structures in the same individual

• Dioecious - has seperate male and female individuals, each has one

Describe hermaphroditism?

• Single animal has both male and female reproductive organs

• Increase reproductive success of places with infrequent mates

• Can change sex during lifetime

• Allows for genetic advantages

Describe gametogenesis?

• Diploid germ cells produce haploid gametes through meiosis

• Spermatogenesis occurs in testes and produced large number of motile sperm cells

• Oogenesis occurs in ovaries and produces few nutrient rich eggs

• Meiosis reduces chromosome number in half and creates genetic variation through crossing over and independent assortment

• Hormones such as testosterone and oestrogen regulate gamete production

Describe fertilisation?

• Fusion of haploid sperm and haploid egg to diploid zygote

• Occur through external or internal fertilisation

• Sperm contains paternal DNA and egg contains maternal DNA

• Fertilisation activates embryonic development, initiates rapid cell division

• Describe embryonic development?

• zygote undergoes mitotic cell divisions

• Cells become specialised through differentiation through organogenesis

• Environmental conditions can influence survival

Describe the ways asexual reproduction occurs in plants?

1. Fragmentation

2. Vegetative propagation

3. Apomixis

Describe fragmentation?

• Piece of parent plant breaks off and grows into new, genetically identical individual

• E.g algae

Describe vegetative propagation?

• New plants grow from specialised vegetative structures such as stems

• E.g runners, rhizomes

Describe Apomixis?

• Seeds form without fertilisation or meiosis

• Offspring clone of mother

• E.g dandelion

Describe the process of sexual reproduction in flowering plant?

• Pollination

• Fertilisation

• Seed formation

• Double fertilisation

Describe pollination?

• Transfer of pollen from anther to stigma

• Self pollination is same plant

• Cross pollination is different plant

• Via wind, insects

Describe fertilisation?

• Zygote becomes embryo

• Endosperm nucleus becomes endosperm

• Ovule becomes seed

• Integuments become seed coat

• Ovary becomes fruits

Describe seed formation?

• Contains embryo, food store

Describe double fertilisation?

• Sperm 1 fuses with egg to become zygote

• Sperm 2 fuses with 2 polar nuclei to become tripod endosperm nucleus, nutritive tissue

• Ensures plant invest enegry

• Improves seed development and survival

Describe bryophytes?

• Reproduce using spores

• Requires water for fertilisation for sperm to swim

• Haploid stage is dominant

• Little protection for embryos

Describe seedless vascular plants?

• Reproduce with spores

• Have vascular tissue allowing for growth

• Fertilisation depends on water

• Diploid stage is dominant

Describe gymnosperms?

• Reproduce using seeds

• Pollen carries sperm

• Greater protection of embryo

Describe angiosperms?

• Reproduce with seeds enclosed in fruits

• Use flowers to facilitate pollination

• Double fertilisation produces both embryo and nutrient issue

• Most efficient and diverse reproduction