Briefly explain why each of the following theories is...

Key Concepts

Pangenesis

Pangenesis was an early theory of heredity that proposed all parts of an organism's body contribute small particles to the germ cells, carrying traits from the parent to the offspring. This concept is outdated because modern genetics shows that inheritance is based on DNA, organized into chromosomes, and that traits are transmitted through genes rather than by hypothetical particles from every cell.

Preformationism

Preformationism is the belief that organisms develop from a miniature version of themselves already present in the sperm or egg. This theory has been disproven by developmental biology, which demonstrates that the embryo is formed through complex processes of cell division and differentiation rather than by the unfolding of a preformed miniature organism.

Blending Inheritance

Blending inheritance suggested that offspring are a smooth mixture of parental traits, implying that genetic variation would be diluted over generations. This idea has been replaced by the particulate theory of inheritance established by Mendel's work, which shows that discrete genes are passed on intact, preserving genetic variation over generations.

Inheritance of Acquired Characteristics

The inheritance of acquired characteristics proposed that traits gained during an organism's lifetime could be passed on to its offspring. This theory is inconsistent with modern genetic understanding, which demonstrates that the DNA sequence is not altered by an organism's experiences or environmental exposures in a way that would be inherited.

Transcript

00:01 This question asks us to briefly explain why each of the following theories is incorrect.

00:05 So for a, we are given pangenesis.

00:08 So we know that pangenesis is going to refer to the whole body approach, where each body cell will be responsible for transferring genetic information to each corresponding body cell of the offspring.

00:48 However, we know that this is not true because if we look at how these offspring are produced, even if this is a mitotic division, asexual reproduction, and specifically in sexual reproduction, we find that our offspring are going to arise from a zygo, so from a unicellular, or it's going to be a zygo, it's going to be the union of a sperm and an egg, but those are haploid, so they become one diploid cell when fertilization occurs.

01:20 So basically from this one cell, we are going to have the 30 trillion cells that make up the adult human beings.

01:29 So all cells are going to originate from one cell.

01:32 It's not going to be that each body cell is going to code for each body cell of the offspring.

01:37 So we're not going to produce any changes that.

01:42 That have been made to, let's say, the finger, the pinky finger of the parent, just because that pinky finger might have been damaged in some way during the parent's lifetime will not mean that the offspring's pinky finger will also be damaged.

01:56 So, pangenesis is going to be incorrect.

01:59 Pre -formationism, which states that there's going to be a preformed miniature adult in either the egg or the sperm.

02:15 That is going to be incorrect due to the fact that, of course, if we are to use microscopy, we do not see a preformed miniature adult within those gametes.

02:27 Instead, we know that fertilization occurs...

Please give Ace some feedback