9A sexual vs asexual reproduction

what is reproduction

the biological process by which organisms produce offspring, ensuring the continuation of the species across generations

asexual reproduction

the process where one parent produces genetically identical offspring (clones) from a single parent, without the fusion of gametes.

eg bacteria, some fungi, some plants

budding (asexual) 

budding occurs when an outgrowth, or bud, on the parent body develops enough to survive on its own and then detaches as a separate organism

eg jellyfish, coral, yeast, hydra, and worms 

fragmentation (asexual) 

occurs  when a piece of the parent body breaks off and both sections regrow into two separate (identical) organisms 

eg sea stars, coral, sponges and many plants 

vegetative propogation (asexual)

occurs when a cutting is taken from a mature parent plant, and the cutting is planted into its own soil to grow into a new independent (identical) plant.

sporogenisis (asexual)

occurs when an organism makes spores that are released into the environment, like into water or air, where they can grow into a new identical organism

eg fungi, ferns, mosses some algae and bacteria

parthogenesis (asexual) 

when an embryo grows from an unfertilised egg (sometimes called virgin birth). The eggs are made by mitosis (diploid) so the new organism is genetically identical to the female parent. this is very rare, only in vertebrate species. 

what are advantages and disadvantages of asexual reproduction

adv:

fast reproduction - no mating means fast reproduction, allowing organisms to rapidly colonise environments with lots of recourses

low energy cost - no energy is spent finding a mate, producing gametes, or raising offspring.

useful traits are cloned - offspring inherit alleles that are already well suited to survive in the current environment

dis:

lack of genetic diversity - producing clones means all offspring have the same alleles. this makes the whole population vulnerable in changing or unpredictable environments.

what is sexual reproduction

the process where a male (haploid) gamete and female (haploid) gamete fuse together in fertilization to create genetically different diploid offspring

more risky and time consuming than asexual, but creates genetic diversity which helps species survive and adapt to changes in their environment

why is genetic diversity important?

helps a species survive for a long time. acts like protection against changes in the environment, such as diseases, predators, climate change, radiation, or natural disasters. bigger gene pool = more genetic diversity, which gives the species a higher chance of surviving when the environment changes. 

sexual reproduction advantages and disadvantages

adv:

creates genetic diversity - offspring inherit a mix of alleles from their parents, meaning some individuals may have traits that help them survive better if the environment changes.

reduces risk of inheriting harmful genetic disorders - recombination of genes can separate ‘bad’ alleles from each other.

dis:

slow and requires more energy - finding a mate, producing gametes, raising offspring (in some species) takes a lot of time and resources

risk of STIs - due to sexual intercourse

risk of embryo damage during development

what are reproductive strategies 

courtship rituals

mating behaviours 

types of fertilisation 

mode of embryonic development 

different reproductive strategies have evolved to help species increase their chances of successful reproduction 

what are the types of fertilisation

external: when sperm and egg fuse outside the body, typically in water.

internal: when the sperm and egg fuse inside the female’s body

what are the modes of embryonic development

viviparity = embryo develops inside the mother’s uterus

eg human

oviparity = embryo develops in eggs laid outside the body

eg chicken

ovoviviparity = embryo develops inside eggs inside the mother

eg shark 

what are courtship rituals 

actions or signals animals use to attract a mate and show they are healthy and ready to breed 

eg of courtship: sounds (like bird or frog calls), movements (danceS), scents (pheromones) colour changes or body displays

what are mating behaviours

the act of sexual reproduction after successful courtship

mating behaviours have evolved to increase the chance of successful (internal or external) fertilisation