Category Archives: reproduction

Reproductive Strategies

antechinus

Image source

Living organisms have evolved many different reproductive strategies to ensure their survival from generation to generation. Scientists sometimes categorize these strategies as “r-selected” (rapid, related to rate) or “K-selected” (related to carrying capacity). You can read a good comparison of r and K-strategies here: Reproductive strategies

Read the ABC Science article: Antechinus go out with a bang and then do “Part B: A case study in reproductive behaviour” on page 150 of your Jacaranda Activity Manual. If you finish, please do the Chapter 12 Review questions and the Activity manual “In Review” for Chapter 12.

Term 2 – Week 5: Reproduction (Year 11)

asexual_sexual_reproduction

This week in Year 11 Biology we are starting to discuss another body system – the reproductive system. First we will study the concepts of asexual and sexual reproduction and then learn how reproduction occurs in unicellular and multicellular organisms.

Asexual Reproduction – Plants, bacteria and fungi

Draw a diagram to show each of the following types of asexual reproduction:

  • binary fission (eg. bacteria, some algae)
  • budding (eg. yeast, hydra)
  • bulbs (eg. daffodils)
  • runners and rhizomes (eg. strawberries)
  • fragmentation (eg. sea stars, flatworms)
  • spore formation (eg. fungi)
  • parthenogenisis (eg. stick insects, some reptiles)

This YouTube video, Asexual Reproduction, shows budding in Hydra and Anenomes and binary fission in Paramecium, as well as asexual reproduction in Volvox, a green algae.

Sexual Reproduction Handout

Week 8: Unit 4: Continuity and Change

Sky_spectral_karyotype

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Area of Study 1: Heredity

This area of study focuses on molecular genetics and the investigation not only of individual units of inheritance, but also of the genomes of individuals and species. Students investigate inheritance in asexually reproducing organisms and the mechanism and patterns of transmission of heritable traits in sexually reproducing organisms.

Students examine the process of meiosis in terms of inputs and outputs and, in accounting for variations in offspring, consider the interplay between genotype and environmental factors, the significance of mutations in DNA, and the relationship between alleles.

All prokaryotes reproduce asexually, without the formation and fusion of gametes. Many plants and fungi also reproduce asexually, meaning that they are genetically identical to their parent. Types of asexual reproduction include:

  • Binary fission (bacteria)
  • Budding (yeast)
  • Vegetative reproduction (strawberry runners, aloe)
  • Sporulation (fungi, algae, ferns)
  • Fragmentation (annelids, sea-stars)
  • Parthenogenesis (some lizards, sharks and stick-insects)

This week we will begin to study molecular genetics – the foundations of ‘who we are’, before environmental factors play a role. Half your DNA comes from your mother (eggs produced in the ovaries) and half from your father (sperm produced in the testes). This DNA contains genes and genes code for proteins, so the gametes (eggs and sperm) contain the genetic instructions that cross the generation gap, giving you the characteristics that you share with your biological parents.  The genetic instructions in an organism make up it’s genotype, which is expressed visually as the phenotype (physical, biochemical and physiological traits).

Humans have 23 pairs of chromosomes, often referred to as the diploid number or 2n=46. The image above is called a karyotype, used to assist with chromosomal analysis – is this one from a male or female? Chromosomes can be distinguished by their relative size, position of the centromere and the patterns of light an dark bands. Matching pairs are said to be homologous. A human male has non-homologous sex chromosomes (XY).

More Resources for this Unit:

 

12: Reproductive Adaptations

Learning Intention: Students will understand the benefits and energy costs of a range of reproductive adaptations. They will compare ‘r’ and ‘K’ strategies and learn how they assist survival of the species.

Success Criteria: Students will be able to describe various reproductive strategies in plants and animals and explain how they assist survival of the species.

Chapter 7: Sexual and Asexual Reproduction

Vegetative-reproduction 

This week we are starting the topic “Reproduction” by looking at Asexual methods of reproduction. In plants, asexual reproduction is also called vegetative reproduction.  Complete the table titled “Types of Vegetative Reproduction” using your text and activity manual. Plants that are produced by vegetative reproduction are genetically identical to their parent plants, which is a very useful trait for horticulturalists. They may use the following methods:

  • Runners (strawberries, water hyacinth)
  • Cuttings (geraniums, roses)
  • Rhizomes (underground stems, as in ferns, irises, ginger and galangal)
  • Tubers (potatoes)
  • Bulbs (daffodils, tulips, onions)
  • Suckers (underground stems that arise a distance from the parent plant eg. elm trees and blackberries)

Some other organisms also reproduce asexually: (Asexual reproduction in Animals)

  • Binary fission (Paramecium, bacteria)
  • Budding (Hydra)
  • Fragmentation (Planarians)
  • Regeneration (Echinoderms such as seastars)
  • Parthenogenisis (some lizards, aphids)

This is a useful Powerpoint presentation to learn about the methods of asexual reproduction:

Amazing Reproductive Strategies

weedy_sea_dragon

Image Source

Tonight on ABC1 you may have been lucky enough to watch “Life” narrated by David Attenborough. This, the first of three episodes, was about fish – their variety, feeding and reproductive behaviours, habitats and predators.  It began with footage taken in southern Australian waters, of the weedy sea dragon, showing how the male and female court by ‘dancing’ then the female transfers the fertilized eggs to the male, who looks after them until they hatch. The tiny hatchlings wriggle free from the father’s belly-fold and begin to feed, with their yolk sac still attached. The anglerfish has another unusual method of reproduction, in which the male is ‘parasitic’ on the female. The tiny male embeds itself in the female and disintegrates into the female’s flesh, until all that is left is the testes.

praying_mantids

Praying mantids exhibit another unusual method of reproduction, in which the male has a good chance of his head being bitten off during mating. If the male happens to lose his rigid grip from atop the female, he is at risk of sexual cannibalism – the female gets a nutritous meal as well as continued copulation, as the nerves that stop copulation are in the head, and the nerves that continue copulation are in the abdomen. Dragonflies and damselflies also display unusual courtship. Eggs may be deposited underwater, drilled into mud, carved into stems, or dropped while in flight.

green_spoonworm

The green spoonworm (Bonellia viridis) is another species in which the female dominates – in fact you are unlikely to find a male spoonworm at all. The spoonworms begin life as free-swimming larvae, which settle to the bottom of the Mediterranean Sea and slowly develop. If the larvae happen to settle on another female, the female releases a chemical that turns the larvae into a tiny male, which migrates through her mouth into the uterus and assumes a parasitic existence. The female can have up to twenty tiny males inside her genital sac, so she expends no energy looking for a mate, while the male benefits by having a safe and secure space, relying on the female for nutrition.

marmosets

Marmosets…………..

gouldian_finch

In a recent article in The Age, “Cheating is risky, but worth it, for female finches”, Adam Carey writes about the reproductive strategies of the beautiful Gouldian Finches, which have an unusually high rate of intra-species incompatability. “Gouldian finches mate two to four times a day during breeding season, but given the opportunity, the female will covertly cuckold her mate, also going to great lengths to keep it a secret. Males will help to incubate eggs and feed chicks, unless the female’s infidelity becomes known, in which case he might abandon the brood.” So what motivates the female to take such a risk? Scientists believe that the female can choose genetically superior mates and maximizes her chance of conceiving healthy offspring by ‘cheating’ on her mate. A superior male can fertilize up to 75% of a female’s eggs, making even one copulation worthwhile.

Mating behaviour in animals – monogamy, polygamy, polygyny and polyandry.

Sexual Reproduction

mandarin fish mating

Image Source

Today we finished our unit on Reproduction by looking at the variety of strategies that vertebrates use to produce offspring. From broadcast spawning (in most fish) where eggs and sperm are released into the aquatic environment, to the production of amniotic eggs in birds and the vivaporous births of mammals, there are different degrees of resources put into reproduction. Different species of sharks show a variety of different strategies from external egg development (oviparous) to placental live birth (viviparous) to internal egg development with live birth (ovoviviparous) to interuterine cannibalism. Terrestrial organisms require internal fertilisation to protect the gametes from dessication and allow the embryo to form either protected by a shell or within the uterus or womb.

Try this student activity to compare asexual and sexual reproductive strategies. More about reproduction here. Check out the wiki for more activities and information.

Asexual Reproduction

asexual reproduction - hydra

This picture shows asexual reproduction in a hydra by budding. Below is an image showing asexual reproduction in green algae by binary fission. The advantages of asexual reproduction are that it can occur quickly and easily without the difficulty of finding a mate. So in favourable conditions, organisms can reproduce many genetically identical offspring that are well suited to their environment. However, the disadvantages are that there is very little variation in the community, so when environmental conditions change, these organisms may not be able to survive. Sexual reproduction produces much varation, allowing for different environmental conditions.

Video from Britannica.com: Plant reproduction – Asexual Reproduction

Visual Glossary of terms: Asexually Reproducing Organisms

asexual reproduction - algae

Vegetative Reproduction

Vegetative reproduction

Image Source

This week we are starting the topic “Reproduction” by looking at vegetative or asexual methods of reproduction. Complete the table titled “Types of Vegetative Reproduction” using your text and activity manual. Plants that are produced by vegetative reproduction are genetically identical to their parent plants, which is a very useful trait for horticulturalists. They may use the following methods:

  • Runners (strawberries, water hyacinth)
  • Cuttings (geraniums, roses)
  • Rhizomes (underground stems, as in ferns, irises, ginger and galangal)
  • Tubers (potatoes0
  • Bulbs (daffodils, tulips, onions)
  • Suckers (undersground stems that arise a distance from the parent plant eg. elm trees and blackberries)

Plant Reproduction

red flower

Photo Source

This bright red flower shows clearly the stamens with anthers attached, where the pollen is distributed from. As insects don’t see colours in the red-orange spectrum, this flower is more likely to be pollinated by birds or mammals (such as possums, bats or small rodents). Wind pollinated plants (such as grasses and conifers) produce large amounts of very small-grained, lightweight pollen. Most flowering plants produce smaller amounts of pollen that is transfered by vectors. They attract vectors with bright colours, alluring aromas or sweet or protein-rich nectar.

If you have access to YouTube, there are some incredible time-lapse photography vidoes showing corn seed and sunflower seed germination (geotropism) at http://www.youtube.com/watch?v=iFCdAgeMGOA&feature=player_embedded Top 10 Amazing Biology Videos: http://www.wired.com/wiredscience/2008/11/top-10-amazin-1/ 

Top 10 Time-lapse videos here: http://www.wired.com/wiredscience/2009/03/tenlapse/